Question

7. A can finish a piece of work in 12 hours while B can finish it in 15 hours. How long will
both take to finish it, working together?
(a) 9 hours
2
3.
(b) 6 hours (c) 6-hours
(d) 8 – hours
3
4
ʜᴏᴡ?​

Answer 1

Answer:

If A can finish a work in 12hours, in one hour, he can do 1/12th of the work.

Similarly, B can finish the same work in 15 hours, so he can do 1/15th of the work in 1 hour.

Now if they work together, in one hour, they both can do 1/12 + 1/15 = 27/180 = 3/20th of the work together.

Therefore, no. of hours it'll take to finish the complete work will be 20/3 hours = 6 2/3 hours = 6 hours and 40 minutes.

(Just check which option, because they're repeated in the question you've given)