A works twice as fast as B. If B can complete work in 12 days independently, then the number of days in which A and B can together finish the work is:

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4 days

6 days

8 days

18 days

answer is A.

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Detailed Solution

Concept- To begin, use the fact that A is twice as fast as B to assume that A takes six days to complete the assignment. Then compute the amount of work done individually by A and B in one day. The total amount of work done by A and B in 1 day is then calculated by dividing 1 by the total amount of labour done by both in 1 day to obtain the answer.
Ratio of rates of working of

and

.
So, ratio of times taken

.
B's 1 day's work

A's one day's work

times the work of

's one day's work

So,

and

together we can finish the work in 4 days.
Hence, the correct answer is option 1.

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