Mesto wrote:

A is 1.5 times as fast as B. A alone can do the work in 20 days. If A and B work on alternative days, beginning with A, in how many days will the work be completed?

A) 23

B) 22

C) 21

D) 24

E) 25

Using ratios can help too.

Ratio of speed = 1.5:1= 3:2

Ratio of time taken = 2:3

So B alone takes 30 days

Together, working alternate days, the two of them complete 1/20 + 1/30 = 5/60 of the work every 2 days.

So they take (60/5 = 12)*2 = 24 days to complete the work.

Answer (D)

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Karishma

Veritas Prep GMAT Instructor

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