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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?
Most Upvoted 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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Community Answer
A and B together can complete a work in 12 days. A alone can complete ...
Given:
A and B together can complete a work in 12 days.
A alone can complete the work in 20 days.

To find:
In how many days A and B together will complete the work if B does the work only for half a day daily.

Solution:
Let's assume that the total work is represented by 'W'.

Work done by A in 1 day = 1/20th of the total work (W)
Work done by B in 1 day = 1/xth of the total work (W), where x represents the number of days it takes for B to complete the work if B works for the whole day.

Work done by A and B together in 1 day = 1/12th of the total work (W)

From the given information, we can form the following equation:

1/20 + 1/x = 1/12

To solve this equation, we need to find a common denominator:

12x + 12(20) = 20x

240 = 8x

x = 30

So, it would take B 30 days to complete the work if B works for the whole day.

But in this case, B works only for half a day daily.

Work done by B in half a day = 1/(2x)th of the total work (W)

Now, let's find the work done by A and B together in 1 day when B works for half a day daily:

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

where y represents the number of days it takes for A and B together to complete the work.

To solve this equation, we need to find a common denominator:

2x + 20 = 20x

20 = 18x

x = 20/18 = 10/9

So, it would take A and B together 10/9 days to complete the work.

But we need to convert this into a whole number of days:

10/9 = 1 + 1/9

So, A and B together will complete the work in 1 day and 1/9th of a day.

Hence, the answer is 10 + 1/9 = 11 days.

Therefore, option (d) 11 days is the correct answer.
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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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