RS Aggarwal Class 7 Math Ninth Chapter Unitary Method Exercise 9B Solution

RS Aggarwal Class 7 Math Ninth Chapter Unitary Method Exercise 9B Solution

EXERCISE 9B

(1) If 48 men can dig a trench in 14 days, how long will 28 men take to dig a similar trench?

(2) 16 men can reap a field in 30 days. How many men must be engaged to reap the same field in 24 days?

(3) 45 cows can graze a field in 13 days. How many cows will graze the same field in 9 days?

(4) 16 horses can consume a certain quantity of corn in 25 days. In how many days same quantity be consumed by 40 horses?

(5) A girl can finish a book in 25 days if she reads 18 pages of it every day. How many days will she take to finish it, if she reads 15 pages every day?

(6) Reeta types 40 words per minute and takes 24 minutes to type a certain document. Her friend Geeta has a typing speed of 48 words per minute. In how much time, will she able to type the same document?

(7) A bus covers certain distance in 3 hours 20 minutes at an average speed of 45 km/h. How long will it take to cover the same distance at a speed of 36 km/h?

(8) At the beginning of a month, a factory has enough materials to make 240 tonnes of steel in a month. If 60 more tones of steel is to be made that month, how long will the materials last?

(9) A contractor employed 210 men to build a house in 60 days. After 12 days, he was joined by 70 more men. In how many days will the remaining work be finished?

(10) A military camp has provisions for 630 men to last for 25 days. How many men must vbe transferred to another camp so that the food lasts for 30 days?

Therefore, number of men transferred is (630 – 525) = 105 men.

(11) a group of 120 men had provisions for 200 days. After 5 days, 30 men died due to an epidemic. How long will the remaining food last?

(12) 1200 soldiers in a fort had enough food for 28 days. After 4 days, some soldiers were transferred to another fort and thus the food lasted for an extra 32 days. How many soldiers left the fort?