Exercise 7C
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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