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A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?
  • a)
    10 days
  • b)
    20 days
  • c)
    15 days
  • d)
    11 days
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
A and B together can complete a work in 12 days. A alone can complete...
  • Work done by A in one day = 1/20. o B's 1 day's work (1/12 - 1/20) = (2/60)= 1/30.
  • B's half day work = (1/30)/2 = 1/60
  • A and B 's one day work (if B work for half day) = (1/20 + 1/60) = (4/60)= 1/15
  • Therefore, total number of days to complete the work = 15 days.
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Most Upvoted Answer
A and B together can complete a work in 12 days. A alone can complete...
Given:

A + B = 1/12 ----(1)
A = 1/20

To find:

Number of days A and B together will complete the work if B does the work only for half a day daily.

Solution:

Let us assume that B can finish the work in ‘x’ days.

Therefore, B can finish 1/x of the work in a day.

As B works for only half a day, he will finish 1/2x of the work in a day.

From equation (1), we can write:

1/12 - 1/20 = 1/x - 1/2x

Simplifying this equation, we get:

x = 15

Therefore, B can finish the work in 15 days.

Now, we need to find the number of days A and B together will complete the work.

Let us assume that they take ‘y’ days to complete the work together.

Therefore, in a day, A and B together can finish 1/y of the work.

As A completes 1/20 of the work in a day, B will complete 1/2x of the work in a day.

So, we can write:

1/y = 1/20 + 1/2x

Substituting the value of ‘x’ as 15, we get:

1/y = 1/20 + 1/30

1/y = (3 + 2)/60

1/y = 5/60

y = 12

Therefore, A and B together will complete the work in 12 days.

Hence, the correct option is (c) 15 days.
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A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?a) 10 daysb) 20 daysc) 15 daysd) 11 daysCorrect answer is option 'C'. Can you explain this answer?
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