Question

Two mens can do a piece of work 4 hours and 3 hours respectively . How much time they will take to do a work together?

Answer 1

Let the work be x ;
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First person can do a x amount of work in 4, hour.
Work = x/4

Second one can do same work in 3 hour,
Work = x/3

If they work together ;
Work done =
= x/3 + x/4
= (7/12)x
= x/(12/7)
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Time = 12/7 hr
= 1 hr 34min 17 sec
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Answer 2

in 4 hr man A completes 1 work
therefore in 1 hr man A completes 1/4 work

in 3 hr man B completes 1 work
therefore in 1 hr man B completes 1/3 work

in 1 hr together they complete 1/3+1/4 work=7/12work
A and B complete 7/12 work in 1 hr
thus A and B complete 1 work in 12/7 hr