Question

3. A can do a piece of work in 7 days of 9 hours each and B can do it in 6 days of 7 hours each. How
long will they take to do it working together 8 2/5 hours a day?
(a) 3 days' (b) 4 days (c) 4 1/2 days (d) 5 days (e) None of these​

Answer 1

Answer:

Since A can dothe work in 7 days of 9 hours each, A can do thework in 7*9 = 63 hours. Thus, in 1 hour, A does 1/63 units of work.

Since B can do the work in 6 days of 7 hours each, B can do the work in 6*7 = 42 hours. Thus, in 1 hour, B does 1/42 units of work.

When both of them work together they would do 1/63 + 1/42 units of work in 1 hour. This is nothing but 5/126 units. If 5/126 units of work gets done in 1 hour, the complete work gets done in 1/(5/126) = 126/5 = 252/10 = 25.2 hours.

Since each day is now having 8 hours, 25.2 / 8 would ne the number of days as required.

This is nothing but 3.15 Days.

Thus, when bith A and work together (for 8 hours a day), they would take 3.15 days to finish the job

Step-by-step explanation:

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