Abel can complete a work in 10 days, Ben in 12 days and Carla in 15 days. All of them began the work together, but Abel

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Abel can complete a work in 10 days, Ben in 12 days, and Carla in 15 days. All of them began the work together, but Abel had to leave after 2 days and Ben 3 days before the completion of the work. How long did the work last?

A. 6
B. 7
C. 8
D. 9
E. 10

Answer: B

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VJesus12 wrote:
Sat Jan 23, 2021 1:56 pm
Abel can complete a work in 10 days, Ben in 12 days, and Carla in 15 days. All of them began the work together, but Abel had to leave after 2 days and Ben 3 days before the completion of the work. How long did the work last?

A. 6
B. 7
C. 8
D. 9
E. 10

Answer: B

Solution:

We see that rates of Abel, Ben and Carla are 1/10, 1/12 and 1/15, respectively. If we let x be the number of days the work lasted, we can create the equation:

1/10 * 2 + 1/12 * (x - 3) + 1/15 * x = 1

Multiplying the equation by 60, we have:

12 + 5x - 15 + 4x = 60

9x = 63

x = 7

Answer: B

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VJesus12 wrote:
Sat Jan 23, 2021 1:56 pm
Abel can complete a work in 10 days, Ben in 12 days, and Carla in 15 days. All of them began the work together, but Abel had to leave after 2 days and Ben 3 days before the completion of the work. How long did the work last?

A. 6
B. 7
C. 8
D. 9
E. 10

Answer: B

Source: e-GMAT
Amount of work Carla completed \(+\) Amount of work Abel completed \(+\) Amount of work Ben completed \(=\) Total amount of work completed

\(\dfrac{t}{15} + \dfrac{2}{10} + \dfrac{t-3}{12} = 1 \Longrightarrow t = 7\)

Therefore, B