Question

A can finish a work in 10 days working 6 hours a day.
B can do it in 15 days working 8 hours a day. In how
many days can they finish the same job, working to-
gether 10 hours a day?
a. 4 days b. 7 days c. 6 days d. 8 days​

Answer 1

Answer:

4 days.

Step-by-step explanation:

A can finish work in 10 days working 6hrs a day.

So A's 1 day work working 1 hr = 1/10 * 1/6 = 1/60

B can finish work in 15 days working 8hrs a day.

So B's 1 day work working 1 hr = 1/15 * 1/8 = 1/120

(A+B)'s working together for 1 day working 1 hr = 1/60 + 1/120 = 3/120.

(A+B)'s working 1 day for 10hrs will complete 3 * 10 /120 = 1/4

So A&B working together for 10hrs a day will complete the work in 4 days.

Answer 2

Answer:

(a) 4 days

Step-by-step explanation:

A can finish a work in 10 days working 6 hours a day.

⇒ Total work = 10 x 6 = 60 hours

⇒ 1 hour = 1/60 of the work

B can do it in 15 days working 8 hours a day.

⇒ Total work = 15 x 8 = 120 hours

⇒ 1 hour = 1/120 of the work

Together, A and B:

1 hour = 1/60 + 1/120 = 1/40 of the work

10 hours = 1/40 x 10 = 1/4 of the work

They worked 10 hours a day:

1/4 of the work = 1 day

All of the work = 1 x 4 = 4 days

Answer: (a) 4 days