Time and Work
- Three taps A, B and C together can fill a tank in 6 h. After working 2 h, C is closed and the tank was filled in 8 h more. Find the time in which C alone can fill the tank ?
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Work of (A + B + C) in 1 H = 1 / 6
Work done in 2 h = 2/6 = 1/3
Remaining part of the tank = 1 - 1/3 = 2/3
Time taken by A + B to fill this 2/3rd part of the tank = 8 h
A and B together can fill tank in 12 h (i.e., 8 x 3/2).
Now, we have A, B and C together filling the tank in 6 h and A and B together fill tank in 12 h.
Correct Option: A
Work of (A + B + C) in 1 H = 1 / 6
Work done in 2 h = 2/6 = 1/3
Remaining part of the tank = 1 - 1/3 = 2/3
Time taken by A + B to fill this 2/3rd part of the tank = 8 h
A and B together can fill tank in 12 h (i.e., 8 x 3/2).
Now, we have A, B and C together filling the tank in 6 h and A and B together fill tank in 12 h.
Work done by C alone in 1 h = 1/6 - 1/12 = 1/12
Hence, C alone can fill the tank in 12 h.
- Sonu can do a piece of work in 20 days. He started the work and left after some days, when 25% work was done. After it Abhijeet joined and completed it working for 10 days. In how many days Sonu and Abhijeet can do the complete work, working together?
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Efficiency of Sonu = (100/20) = 5%
Rest work = 75%
∴ Efficiency of Abhijeet = 75/10 = 7.5%
∴ Combined efficiency of Sonu and Abhijeet = 7.5 + 5 = 12.5%Correct Option: B
Efficiency of Sonu = (100/20) = 5%
Rest work = 75%
∴ Efficiency of Abhijeet = 75/10 = 7.5%
∴ Combined efficiency of Sonu and Abhijeet = 7.5 + 5 = 12.5%
∴ Number of days required by Sonu and Abhijeet, to work togethere = 100/12.5 = 8days
- X is 4 times more efficient as Y , then the number of days taken by X and Y are in the ratio ?
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Efficiency (X : Y) = 5 : 1
No. of days (X : Y) = 1 : 5Correct Option: B
Efficiency (X : Y) = 5 : 1
No. of days (X : Y) = 1 : 5
- A alone can complete a work in 18 days and B alone in 15 days. B alone worked at it for 10 days and then left the work. In how many more days, will A alone complete the remaining work ?
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Part of work done by B in 10 days
= 10 × 1 = 2 15 3 Remaining work = 1 - 2 = 1 3 3 ∴ Time taken by A = 1 × 18 = 6 days 3 Correct Option: C
Part of work done by B in 10 days
= 10 × 1 = 2 15 3 Remaining work = 1 - 2 = 1 3 3 ∴ Time taken by A = 1 × 18 = 6 days 3
- A can do a piece of work in 20 days and B in 30 days. They work together for 7 days and then both leave the work. Then C alone finishes the remaining work in 10 days. In how many days will C finish the full work ?
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Work done by A and B in 7 days.
= 7 + 7 20 30 = 21 + 14 = 35 = 7 60 60 12
So, Remaining work= 1 - 7 = 5 12 12
∴ Time taken by C= 12 × 10 = 24 days. 5 Correct Option: C
Work done by A and B in 7 days.
= 7 + 7 20 30 = 21 + 14 = 35 = 7 60 60 12
So, Remaining work= 1 - 7 = 5 12 12
∴ Time taken by C= 12 × 10 = 24 days. 5
