Class-7 Maths Chapter-4 Exercise 4.2 Simple equations

EVENTS CONVENT HIGH SCHOOL

12/01/2021                       CLASS-7                                  SLOT-2

MATHS

Chapter-4 SIMPLE EQUATIONS

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Exercise-4.2 

Question 1:Give first the step you will use to separate the variable and then solve the equation:

(a) x + 1 = 0 (b) x + 1 = 0 (c) x − 1 = 5

(d) x + 6 = 2 (e) y − 4 = − 7 (f) y − 4 = 4

 

Answer:(a) x − 1 = 0

Adding 1 to both sides of the given equation, we obtain

x − 1 + 1 = 0 + 1

x = 1

(b) x + 1 = 0

Subtracting 1 from both sides of the given equation, we obtain

x + 1 − 1 = 0 − 1

x = −1

(c) x − 1 = 5

Adding 1 to both sides of the given equation, we obtain

x − 1 + 1 = 5 + 1

x = 6

(d) x + 6 = 2

Subtracting 6 from both sides of the given equation, we obtain

x + 6 − 6 = 2 − 6

x = −4

(e) y − 4 = −7

Adding 4 to both sides of the given equation, we obtain

y − 4 + 4 = − 7 + 4

y = −3

(f) y − 4 = 4

Adding 4 to both sides of the given equation, we obtain

y − 4 + 4 = 4 + 4

y = 8

Question 2:Give first the step you will use to separate the variable and then solve the equation:

(a) 3l = 42 (b)  (c) 

(d) 4x = 25 (e) 8y = 36 (f) 

(g)  (h) 20t = − 10

Answer:

(a) 3l = 42

Dividing both sides of the given equation by 3, we obtain

l = 14

(b) 

Multiplying both sides of the given equation by 2, we obtain

b = 12

(c) 

Multiplying both sides of the given equation by 7, we obtain

p = 28

(d) 4x = 25

Dividing both sides of the given equation by 4, we obtain

x = 

(e) 8y = 36

Dividing both sides of the given equation by 8, we obtain

y = 

(f) 

Multiplying both sides of the given equation by 3, we obtain

(g) 

Multiplying both sides of the given equation by 5, we obtain 

(h) 20t = −10

Dividing both sides of the given equation by 20, we obtain

Question 3:Give the steps you will use to separate the variable and then solve the equation:

(a) 3n − 2 = 46 (b) 5m + 7 = 17 (c) 

(d) 

Answer:

(a) 3n − 2 = 46

Adding 2 to both sides of the given equation, we obtain

3n − 2 + 2 = 46 + 2

3n = 48

Dividing both sides of the given equation by 3, we obtain

n = 16

(b) 5m + 7 = 17

Subtracting 7 from both sides of the given equation, we obtain

5m + 7 − 7 = 17 − 7

5m = 10

Dividing both sides of the given equation by 5, we obtain

(c) 

Multiplying both sides of the given equation by 3, we obtain

Dividing both sides of the given equation by 20, we obtain

(d)

Multiplying both sides of the given equation by 10, we obtain

Dividing both sides of the given equation by 3, we obtain

p = 20

Question 4:Solve the following equations:

(a) 10p = 100 (b) 10p + 10 = 100 (c) 

(d)  (e)  (f) 3s = − 9

(g) 3s + 12 = 0 (h) 3s = 0 (i) 2q = 6

(j) 2q − 6 = 0 (k) 2q + 6 = 0 (l) 2q + 6 = 12

Answer:

(a) 10 p = 100

(b) 10 p + 10 = 100

10 p + 10 − 10 = 100 − 10

10 p = 90

(c) 

(d) 

(e)

(f) 3 s = −9

(g) 3 s + 12 = 0

3 s + 12 − 12= 0 − 12

3 s = −12

(h) 3 s = 0

(i) 2q = 6

(j) 2q − 6 = 0

2q − 6 + 6 = 0 + 6

2q = 6

(k) 2q + 6 = 0

2q + 6 − 6 = 0 − 6

2q = −6

(l) 2q + 6 = 12

2q + 6 − 6 = 12 − 6

2q = 6

Exercise-4.3

Question 1:Solve the following equations.

(a)  (b) 5t + 28 = 10 (c) 

(d)  (e)  (f) 

Answer:

(a) 

 (Transposing to R.H.S.)

Dividing both sides by 2,

(b) 5t + 28 = 10

5t = 10 − 28 = −18 (Transposing 28 to R.H.S.)

Dividing both sides by 5,

(c) 

 (Transposing 3 to R.H.S.)

Multiplying both sides by 5,

a = −1 × 5 = −5

(d) 

 (Transposing 7 to R.H.S.)

Multiplying both sides by 4,

q = −8

(e) 

Multiplying both sides by 2,

5x = −10 × 2 = −20

Dividing both sides by 5,

(f) 

Multiplying both sides by 2,

Dividing both sides by 5,

Question 2:Solve the following equations.

(a) 2 (x + 4) = 12 (b) 3 (n − 5) = 21

(c) 3 (n − 5) = − 21 (d) −4 (2 + x) = 8

(e) 4(2 − x) = 8

Answer:

(a) 2 (x + 4) = 12

Dividing both sides by 2,

x = 6 − 4 = 2 (Transposing 4 to R.H.S.)

(b) 3 (n − 5) = 21

Dividing both sides by 3,

n = 7 + 5 = 12 (Transposing −5 to R.H.S.)

(c) 3 (n − 5) = −21

Dividing both sides by 3,

n = − 7 + 5 = −2 (Transposing −5 to R.H.S.)

(d) −4 (2 + x) = 8

Dividing both sides by −4,

x = − 2 − 2 = −4 (Transposing 2 to R.H.S.)

(e) 4 (2 − x) = 8

Dividing both sides by 4,

2 − x = 2

−x = 2 − 2 (Transposing 2 to R.H.S.)

−x = 0

x = 0

Question 3:

Solve the following equations.

(a) 4 = 5 (p − 2)         (b) − 4 = 5 (p − 2)

(c) 16 = 4 + 3 (t + 2)   (d) 4 + 5 (p − 1) = 34

(e) 0 = 16 + 4 (m − 6)

Answer:

(a) 4 = 5 (p − 2)

Dividing both sides by 5,

(b) − 4 = 5 (p − 2)

Dividing both sides by 5,

(c) 16 = 4 + 3 (t + 2)

16 − 4 = 3 (t + 2) (Transposing 4 to L.H.S.)

12 = 3 (t + 2)

Dividing both sides by 3,

4 = t + 2

4 − 2 = t (Transposing 2 to L.H.S.)

2 = t

(d) 4 + 5 (p − 1) = 34

5 (p − 1) = 34 − 4 = 30 (Transposing 4 to R.H.S.)

Dividing both sides by 5,

p = 6 + 1 = 7 (Transposing −1 to R.H.S.)

(e) 0 = 16 + 4 (m − 6)

0 = 16 + 4m − 24

0 = −8 + 4m

4m = 8 (Transposing −8 to L.H.S)

Dividing both sides by 4,

m = 2

Question 4:

(a) Construct 3 equations starting with x = 2

(b) Construct 3 equations starting with x = − 2

Answer:

(a) x = 2

Multiplying both sides by 5,

5x = 10 (i)

Subtracting 3 from both sides,

5x − 3 = 10 − 3

5 x − 3 = 7 (ii)

Dividing both sides by 2,

(b) x = −2

Subtracting 2 from both sides,

x − 2 = − 2 − 2

x − 2 = −4 (i)

Again, x = −2

Multiplying by 6,

6 × x = −2 × 6

6x = −12

Subtracting 12 from both sides,

6x − 12 = − 12 − 12

6x − 12 = −24 (ii)

Adding 24 to both sides,

6x − 12 + 24 = − 24 + 24

6x + 12 = 0 (iii)

EXERCISE 4.4

Question 1:Set up equations and solve them to find the unknown numbers in the following cases:

(a) Add 4 to eight times a number; you get 60.

(b) One-fifth of a number minus 4 gives 3.

(c) If I take three-fourths of a number and add 3 to it, I get 21.

(d) When I subtracted 11 from twice a number, the result was 15.

Answer:(a) Let the number be x.

8 times of this number = 8x

8x + 4 = 60

8x = 60 − 4 (Transposing 4 to R.H.S.)

8x = 56

Dividing both sides by 8,

(b) Let the number be x.

One-fifth of this number = 

 (Transposing −4 to R.H.S.)

Multiplying both sides by 5,

(c) Let the number be x.

Three-fourth of this number = 

 (Transposing 3 to R.H.S.)

Multiplying both sides by 4, 

Dividing both sides by 3,

(d) Let the number be x.

Twice of this number = 2x

2x − 11 = 15

2x = 15 + 11 (Transposing −11 to R.H.S.)

2x = 26

Dividing both sides by 2,

x = 13

Class-2 EVS Chapter-3 safety Rules

 EVENTS CONVENT HIGH SCHOOL

16/01/2021                         CLASS-2                                  SLOT-2

E.V.S

Chapter-3 SAFETY RULES

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A. Oral Questions:

Que-1 Write the safety rules at home?

Ans-1 We should not play with fire

    b. Never open the door for a stranger

    c. Do not play with sharp objects.

Que-2 Where should we cross the road?

Ans-2 We should cross the road at Zebra Crossing.

Que-3 Draw the raod signs :

Draw the Road Sign

B.Tick the(✔️) correct option:

1. Which of the following is a safety rule on the road?

a. Cross from a zebra crossing (✔️)      b.Play on the road

2. We should not .

a.Board a busi in queur                        b.Get off from a moving bus (✔️)

3. At home, we should not play with

a. Knife and scissors(✔️)                       b. Bat and ball

C.Fill in the blanks

1.We should cross the road from zebra crossing.

2.Wear life jackets when you enter the water.

3.We should not talk with driver.

4.We should stand in a queue to get into bus.

5.We must wear seat belt while driving the vehicle.

Class-3 Science Chapter-3 Soil

EVENTS CONVENT HIGH SCHOOL

16/01/2021                         CLASS-3                                  SLOT-2

SCIENCE

Chapter-3 SOIL

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A.Fill in the blanks:-

1. Sand soil holds the least water.

2. Clay soil hold the most water.

3.loam is a mixture of sand and clay with humus.

4. Plants grow salinity in soil having minerals salts.

5. If plants do not grow well and add fertilizers to the soil.

B. Tick the (✔️)correct option

1.Soil is formed by the breaking up of.

a rocks(✔️)                      b.stones                 c pebbles

2. Humus is generally

a cherry red                   b.dark brown.(✔️)    c.parrot green.

3. Which care one of the following is a chemical fertilizer?

a.Loam.                         b.Clay.                       c.Urea(✔️)

C. Match the following:

1. Stones.              large particles

2. Sand                  tiny particles

3. Clay                  closely packed 

4. Loam                  sand and clay

D.Answer the following questions:-

1.What is a soil formed?

Ans.1Soil is formed by the breaking up of rocks.

Draw the Foramation of Soil

2.What carries the soil from one place to another?

Ans.2 Melting ice rain and strong wind carries the soil from one place to another.

3. Name the different kinds of soil?

Ans.3 gravel,sand, clay and loam are four kinds of soils.

4. What is humus?

Ans.4 Dead leaves and decayed bodies of animals and plants form the humus.

5. Why does water not pass through play?

Ans.5 water does not pass through clay because they are closely packed.

6. Which is the best soil for growing plants?

Ans.6 loam is the Best soil for growing plants.

7. How do farmers make the soil rich?

Ans.7 farmers make the soil rich by adding enrich fertilizers and also use fresh leaves cow dung and animal waste as manure.

Class-8 SCIENCE CHAPTER-3 SYNTHETIC FIBRES AND PLASTICS

 EVENTS CONVENT HIGH SCHOOL

15/01/2021                         CLASS-8                                  SLOT-2

  SCIENCE

CHAPTER -3 SYNTHETIC FIBRES AND PLASTICS

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Question 1.Explain why some fibres are called synthetic.
Answer:All fibres are not natural. Some fibres are man-made. The fibres made artificially are called synthetic fibres.

Question 2.Mark (√) the correct answer:
Rayon is different from synthetic fibres because
(a) it has a silk-like appearance.
(b) it is obtained from wood pulp.
(c) its fibres can also be woven like those of natural fibres.
Answer:
(b) it is obtained from wood pulp.

Question 3.Fill in the blanks with appropriate words:
(a) Synthetic fibres are also called or fibres.
(b) Synthetic fibres are synthesised from raw material called
(c) Like synthetic fibres, plastic is also

Answer:(a) artificial, man-made
(b) petrochemicals
(c) polymer

Question 4.Give examples which indicate that nylon fibres are very strong.
Answer:Nylon fibres are used to make ropes for rock climbing and for parachutes.

Question 5.Explain why plastic containers are favoured for storing food.
Answer:The main advantages of using plastic containers for storing food are:

    (a)  plastic has light weight.

    (b)  lower price 

    (c)  good strength and

    (d)  are easy to handle.

 

Question 6.Explain the difference between the thermoplastic and thermosetting plastics.
Answer:

Question 7.Explain why the following are made of thermosetting plastics.

(a) Saucepan handles
(b) Electric plugs/switches/plug boards.

Answer:(a) Thermosetting plastic does not soften on heating. Also it is a bad conductor of heat. This is why saucepan handles are made of bakelite which is a thermosetting plastic.

(b) Thermosetting plastic cannot be softened on heating. It is a bad conductor of heat as well as electricity. This is why electric plugs/switches/plug boards are made of backelite which is a thermosetting plastics.

Question 8.Categorise the materials of the following products into can be recycled and Cannot be recycled:
Telephone instruments, plastic toys, cooker handles, carry bags, ball point pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches.

Answer:Materials can be recycled: Telephone instruments, plastic toys, ball point pens, plastic bowls. (As these are thermoplastics, so these can be recycled).
Materials cannot be recycled: Cooker handles, carry bags, plastics, covering; on electric wire, plastic chairs, etc. (As these are thermosetting, so cannot be recycled.)

Question 9.Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, a giving your reason.

Answer:I will advise Rana to wear cotton clothes. Synthetic fibres do not absorb water or sweat. They stick to the body in summer and do not allow ventilation of air. Thus, they made us uncomfortable during summer. Cotton clothes which are natural fabric, do not contain heat, instead they reflect out heat. Besides, they also provide aeration. So, during summer, we prefer cotton clothes and not the synthetic clothes.

Question 10.Give examples to show that plastics are noncorrosive in nature.
Answer:The plastics are non-corrosive, that is, they do not react or do not have chemical reaction with the materials contained in it. That is why containers like bucket, mug, water bottles and food containers are made up of plastics.

Question 11.Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.
Answer:Handle and bristles of a tooth brush should be made of different materials because they have different uses and require different properties in the material, for example, bristles should be much more flexible than the handle.

Question 12.Avoid plastics as far as possible’. Comment on this advice.
Answer:Plastic takes several years to decompose. So it is not environment friendly. Burning of plastic releases lots of poisonous gases which cause pollution to the atmosphere. The burning process of plastics is quite slow and it is not burnt completely. Therefore, use of plastics should be avoided as far as possible.

Question 13.Match the terms of column A correctly with the phrases given in column B.

Answer:

A	B
(i) Polyester	(d) Fabrics do not wrinkle easily.
(ii) Teflon	(c) Used to make non-stick cookwares
(iii) Rayon	(a) Prepared by using wood pulp
(iv) Nylon	b) Used for making parachutes and stockings

 

Class-9 SCIENCE Chapter-2 Is Matter around us pure.

 EVENTS CONVENT HIGH SCHOOL

12/01/2021                           cLASS-9                                  SLOT-2

SCIENCE

Chapter-2 IS MATTER AROUND US PURE?

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  Question 1:What is meant by a pure substance?

Answer:A pure substance is the one that consists of a single type of particles, i.e., all constituent particles of the substance have the same chemical nature. Pure substances can be classified as elements or compounds.

 

Question 2:List the points of differences between homogeneous and heterogeneous mixtures.

Answer: A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example: salt in water, sugar in water, copper sulphate in water

A heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example: sodium chloride and iron fillings, salt and sulphur, oil and water

 

Question 3:How are sol, solution and suspension different from each other?

Answer:Sol is a heterogeneous mixture. In this mixture, the solute particles are so small that they cannot be seen with the naked eye. Also, they seem to be spread uniformly throughout the mixture. The Tyndall effect is observed in this mixture. For example: milk of magnesia, mud

Solution is a homogeneous mixture. In this mixture, the solute particles dissolve and spread uniformly throughout the mixture. The Tyndall effect is not observed in this mixture. For example: salt in water, sugar in water, iodine in alcohol, alloy

Suspensions are heterogeneous mixtures. In this mixture, the solute particles are visible to the naked eye, and remain suspended throughout the bulk of the medium. The Tyndall effect is observed in this mixture. For example: chalk powder and water, wheat flour and water

 

Question 4:To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.

Answer:Mass of solute (sodium chloride) = 36 g (Given)

Mass of solvent (water) = 100 g (Given)

Then, mass of solution = Mass of solute + Mass of solvent

= (36 + 100) g

= 136 g

Therefore, concentration (mass by mass percentage) of the solution

 Question 5:How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?

Answer:A mixture of two miscible liquids having a difference in their boiling points more than 25°C can be separated by the method of distillation. Thus, kerosene and petrol can be separated by distillation.

 

Question 6:Classify the following as chemical or physical changes:

Answer:• Cutting of trees → Physical change

• Melting of butter in a pan → Physical change

• Rusting of almirah → Chemical change

• Boiling of water to form steam → Physical change

• Passing of electric current through water, and water breaking down into hydrogen and oxygen gas → Chemical change

• Dissolving common salt in water → Physical change

• Making a fruit salad with raw fruits → Physical change

• Burning of paper and wood → Chemical change

 

Question 7:Name the technique to separate

(i) butter from curd

(ii) salt from sea-water

(iii) camphor from salt

Answer:

(i) Butter can be separated from curd by centrifugation.

(ii) Salt can be separated from sea-water by evaporation.

(iii) Camphor can be separated from salt by sublimation

 

Question 8:Try segregating the things around you as pure substances or mixtures.

Answer:Pure substance: Water, salt, sugar

Mixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food

 

Question 9:What type of mixtures is separated by the technique of crystallization?

Answer:By the technique of crystallization, pure solids are separated from impurities. For example, salt obtained from the sea is separated from impurities; crystals of alum (Phitkari) are separated from impure samples.

 

Question 10: Pragya tested the solubility of three different substances at different temperatures and collected the data as given below( results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).

Substance dissolved	Temperature in K
	283	293	313	333	353
Potassium nitrate	21	32	62	106	167
Sodium chloride	36	36	36	37	37
Potassium chloride	35	35	40	46	54
Ammonium chloride	24	37	41	55	66

(a)  What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?

(b)  Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.

(c)  Find the solubility of each salt at 293 K. What salt has the highest solubility at this temperature?

(d)  What is the effect of change of temperature on the solubility of a salt?

Answer:10  (a) At 313 K, 62 grams of Potassium nitrate dissolved in 100 grams of water. So to produce a saturated solution of potassium nitrate in 50 grams of water, we need 62 x 50 = 31 grams of potassium nitrate 100

(b) Some soluble potassium chloride will separate out in the form of crystals at room temperature because the solubility of potassium chloride will decrease with decrease in temperature.

(c) (i)   Solubility of Potassium nitrate at 293 K is 32 grams. (ii)  Solubility of Sodium chloride at 293 K is 36 grams. (iii) Solubility of Potassium chloride at 293 K is 35 grams. (iv) Solubility of Ammonium chloride at 293 K is 37 grams. The solubility of Ammonium chloride is highest at this temperature.

(d) The solubility of salt increases with increase in temperature

 
Question 11:Classify each of the following as a homogeneous or heterogeneous mixture.

Soda water, wood, air, soil, vinegar, filtered tea

Answer:11 Homogeneous mixtures: Soda water, air, vinegar

Heterogeneous mixtures: Wood, soil, filtered tea