Question

If 20 man or 30 boys can do a piece of work in 36 days, in how many days will 10 men and 12 boys do it? a. 15 C: 30 b. 20 d. 40.

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Answer 1

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Answer:

d. 40 days

Explanation:

If 20 men are equivalent to 30 boys, then half as many, 10 men, are equivalent to 15 boys.

The work output of 10 man and 12 boys is then equivalent to the work output of 15 +12 = 27 boys.

The time required is inversely proportional to the workforce, so 27 boys, instead of 30, will take 30/27 = 10/9 times as long as 36 days to do the work

(10/9)×(36 days) = 40 days

10 men and 12 boys can do the work in 40 days.

Answer 2

40 days

Explanation:

20 men = 30 boys can do the job so

10 men = 15 boys

30 boy hours = 36 days

30 * 36 = 1080 boy days

We have 10 men and 12 boys to do the job

We replace the 10 men with 15 boys

We have 15 boys and 12 boys for a total of 27 boys to do 1080 boy days worth of work

27 * day = 1080 boy days

days = 1080 /27

days = 40