myhelper: S.chand publication New Learning Composite mathematics solution of class 7 Chapter 7 Ratio and Proportion and Unitary Method Exercise 7C

Exercise 7C

OPEN IN YOUTUBE

Question 1

If 30 m of cloth cost Rs. 2400, what is the cost of 50 m cloth?

Sol :

Cost of 30m cloth is 2400

Cost of 50m cloth is $=\frac{2400 \times 50}{30}=4000$

Ans Cost of 50m cloth is 4000

OPEN IN YOUTUBE

Question 2

If 8 ball pens cost Rs. 40, how much will 20 ball pens of the same kind will cost?

Sol :

Ball pens cost 40

20 ball pens cost $\frac{40\times 20}{8}$

=100

Ans : Cost of 20 ball pens is 100

OPEN IN YOUTUBE

Question 3

Find the price of 744 articles at the rate of Rs. 60.25 a dozen.

Sol :

12 articles cost 60.25

744 articles cost $\frac{60.25\times 744}{12}$

=3735.5

Ans : Price of 744 articles is 3735.5

OPEN IN YOUTUBE

Question 4

If the wages of 15 men for 8 days are Rs. 60,000, how much would they receive for 14 days?

Sol :

15 men's wage for 8 days are 60000

15 men's wage for 14 days are $\frac{60000 \times 14}{8}$

=105000

Ans : They receive 105000 in 14 days

OPEN IN YOUTUBE

Question 5

If a car goes 45 m in 3 seconds, how far does it go in 5 seconds? How long does it take in going 120 m?

Sol :

In 3 sec the car goes 45m

In 5 sec the car goes $\frac{45 \times 5}{3}$

=75m

Ans : In 5 sec the car goes 75m

The car goes 45m in 3sec

The car goes 120m in $\frac{3\times 120}{45}$ =8sec

Ans : It take 8sec for going 120m

OPEN IN YOUTUBE

Question 6

If 48 men have ration for 16 days, how long will the food last, if a reinforcement of 16 men arrives?

Sol :

48 men have food for 16 days

48+16=64 men have food for $\frac{16\times 48}{64}$ days

=12 days

Ans : The food will last for 12 days

OPEN IN YOUTUBE

Question 7

How long will 50 men take to do the same job, that 40 men do in 25 days?

Sol :

40 men can do a job in 25 days

40 men can do a job in 25×40 days

50 men can do a job in $\frac{25\times 40}{50}$ days

=20 days

Ans : 50 men can do it in 20 days

OPEN IN YOUTUBE

Question 8

If 10 kg of mangoes cost Rs. 550, how much will 27 kg cost? How many kilograms of mangoes can be bought for Rs. 1925?

Sol :

10 kg of mangoes cost 550

1 kg of mangoes cost $\frac{550}{10}$

27 kg of mangoes cost $\frac{550 \times 27}{10}$

=1485

550 is cost of 10 kg mango

1 is cost of $\frac{10}{550}$ kg mangoes

1925 is cost of $\frac{10 \times 1925}{550}$ =35kg

Ans : Cost of 27 kg mangoes is 1485

35 kg can be bought for 1925

OPEN IN YOUTUBE

Question 9

A garrison of 1200 men has provisions for 60 days. How long will they last, if the garrison (a) is reduced to 600 men; (b) reinforced by 800 men?

Sol :

(a)

1250 men has provisions for 60 days

1 men has provisions for 60×1200 days

600 men has provisions for $\frac{60 \times 1200}{600}$ =120 days

Ans : They last for 120 days

(b)

1200 men has provisions for 60 days

1 men has provisions for 60×1200 days

(1200+800)=2000 men has provisions for $\frac{60\times 1200}{2000}$ =36 days

Ans : They last for 36 days

OPEN IN YOUTUBE

Question 10

On a certain map, 2 cm represent 1 km. What area shows 20 sq cm on the map represent?

Sol :

20 sq cm is the area on the map

Let us consider length and breadth -2 and 10 respectively

2cm×10cm=20 sq cm

Converting in km

2cm $=\frac{2}{2}$ km

10 $=\frac{10}{2}$ km

∴Area $=\frac{2}{2} \times \frac{10}{2}=5$ sq km

Ans : 5 sq km does the map represent

OPEN IN YOUTUBE

Question 11

The greatest safe load for a lift is 14 men, each weighing 80 kg. How many people, each weighing 70 kg, can it take safely?

Sol :

Weight of 80 kg each a safe lift 14 men

Weight of 1 kg each a safe lift 14×80 men

Weight of 80 kg each a safe lift $\frac{14 \times 80}{70}$ =17 men

Ans : It can take 16 men safely

OPEN IN YOUTUBE

Question 12

Five turns of the winder of my watch, keeps it going for 15 hours, What is the effect of 9 turns?

Sol :

5 turns of the winder , keep it going for 15 h

1 turns of the wimder , keep it going for $\frac{15}{5}$ h

9 turns of the winder , keep it going for $\frac{15\times 9}{5}$ =27 h

Ans : In 9 turns its goes 27 h

OPEN IN YOUTUBE

Question 13

24 men can repair a road in 15 days. How long will it take 20 men to do so, if all, work at the same rate?

Sol :

24 men can repair a road in 15 days

1 men can repair a road in 15×24 days

20 men can repair a road in $\frac{15 \times 24}{20}$ =18 days

Ans : 20 men can do it in 18 days

OPEN IN YOUTUBE

Question 14

I have enough money to take a 24 days holiday, If i spend Rs. 125 a day. How long a holiday can I take, if I spend Rs. 150 a day?

Sol :

If I spend 125 a day then I can take 24 holidays

If I spend 1 a day then I can take 24×125 holidays

If I spend 150 a day then I can take $\frac{24 \times 125}{150}$ =20 holidays

OPEN IN YOUTUBE

Question 15

A man walks 110 m in a minute. How long will he take to walk 26.4 km?

Sol :

26.4 km=26400 m

A man walks 100m in a 1m

A man walks 1m in a $\frac{1}{110}$ m

A man walks 26400m in a $\frac{26400}{110}$ =240 m or 4 h

Ans : He takes 4 h to walk 26.4 km

S.chand publication New Learning Composite mathematics solution of class 7 Chapter 7 Ratio and Proportion and Unitary Method Exercise 7C

Exercise 7C

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

No comments:

Post a Comment

Contact Form