13. A can do a piece of work in 14 days which B can do in 21 days. They begin together but 3 days
before the completion of the work. A leaves off. The total number of days to complete the work is
6-day's
5 days
10-days
10
ܘܘ 135
days
2
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Answer:
Step-by-step explanation:A’s one day work =1/14
B’s one day work=1/21
(A+B)’s one day work =1/14+1/21=(3+2)/42 =5/42
(A+B) can do the work in =42/5 =8.4 days
They work together in =(8.4–3)= 5.4days
Work done by both in 5.4 days =(5/42)×5.4
=5×54/42×10= 9/7×2= 9/14 work.
Remaining work =1- 9/14=5/14.
1 work B can do in = 21 days
5/14 work B can do in =21×5/14 =15/2=7.5 days
Total days to complete the work=5.4+7.5
=12.9 days or 13 days. Answer.
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