two men can do a peice of work in 6hours and 4hours respectively. after the first has worked for 2 hours, he is joined by other. by when should work be completed
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6
1st person can do 1 work in 6 hours
In 1 hour he does: 1/6 part of work
2nd person can do the same work in 4 hours
In 1 hour he does: 1/4 part of work.
1st person worked for 2 hours.
In 2 hours he did: 2*1/6 = 1/3 part of work
Work Remaining = 1 - 1/3 = 2/3 work
Now both the persons are working
In 1 hour both do: 1/6 + 1/4 = 2+3/12 = 5/12 work
1 hour== 5/12 work
X hours = 2/3 work
5X/12 = 2/3
X = 1.6 hours...
Hence the work will be completed in another 1.6 hours.
Hope it helps
Answered by
8
Answer is . 1 h and 36min
A 1 he work=1/6
B 1 he work=1/4
When A worked for 2 hours:
=2×1/6=1/3
Remaining= 1-1/3=2/3
(A+B) 1 hr work = 1/6+1/4
=2+3/12=5/12
Total work completed=2/3÷5/12
=2/3×12/5=8/5
8/5=1³/5×60 min =1 hr 36 min
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