# RS Aggarwal Class 8 Math Thirteenth Chapter Time and Work Exercise 13B Solution

## EXERCISE 13B

### OBJECTIVE QUESTIONS

#### Tick (√) the correct answer in each of the following:

**(1) A alone can do a piece of work in 10 days and B alone can do it in 15 days. In how many days will A and B together do the same work? **

Ans: (b) 6 days

**(2) A man can do a piece of work in 5 days. He and his son working together can finish it in 3 days. In how many days the son do it alone?**

Ans: (c) 7(1/2) days

**(3) A can do a job in 16 days and B can do the same job in 12 days. With the help of C, they can finish the job in 6 days only. Then, C alone can finish it in**

Ans: (d) 48 days

**(4) To complete a work, A takes 50% more time than B. If together they take 18 days to complete the work, how much time shall B take to do it?**

Ans: (a) 30 days

**(5) A works twice as fast as B. If both of them can together finish a piece of work in 12 days, then B alone can do it in**

Ans: (c) 36 days

**(6) A alone can finish a piece of work in 10 days which B alone can do in 15 days. If they work together and finish it, then out of total wages of Rs 3000, A will get**

Ans: (c) Rs 1800

**(7) The rates of working of A and B are in the ratio 3 : 4. The number of days taken by them to finish the work are in the ratio**

Ans: (c) 4 : 3

**(8) A and B together can do a piece of work in 12 days; B and C can do it in 20 days while C and A can do it in 15 days. A, B and C all working together can do it in**

Ans: (c) 10 days

**(9) 3 men or 5 women can do a work in 12 days. How long will 6 men and 5 women take to do it?**

Ans: (c) 4 days

**(10) A can do a piece of work in 15 days. B is 50% more efficient than A. B can finish it in **

Ans: (a) 10 days

**(11) A does 20% less work than B. If A can finish a piece of work in 7(1/2) hours, then B can finish it in**

Ans: (c) 6 hours

**(12) A can do a piece of work in 20 days which B alone can do in 12 days. B worked at it for 9 days. A can finish the remaining work in**

Ans: (b) 5 days

**(13) A can do a piece of work in 25 days, which B alone can do in 20 days. A started the work and was joined by B after 10 days. The work lasted for**

Ans: (c) 16(2/3) days

**(14) Two pipes can fill a tank in 20 minutes and 30 minutes respectively. If both the pipes are opened simultaneously, then the tank will be filled in**

Ans: (b) 12 minutes

**(15) A tap can fill a cistern in 8 hours and another tap can empty the full cistern in 16 hours. If both the taps are open, the tome taken to fill cistern is**

Ans: (c) 16 hours

**(16) A pump can fill a tank in 2 hours. Due to a leak in the tank it takes 2(1/3) hours to fill the tank. The leak can empty the full tank in**

Ans: (d) 14 hours

**(17) Two pipes can fill a tank in 10 hours and 12 hours respectively, while a third pipe empties the full tank in 20 hours. If all the three pipes operate simultaneously, in how much time will the tank be full? **

Ans: (b) 7 hrs 30 min

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