Question

6. Two men can do a piece of work in 6 hours and 4 hours respectively. After the first has worked for 2
hours, he is joined by the other. By when should the work be completed ?​

Answer 1

work first man can do in one hour= 1/6

work second man can do in one hour = 1/4

so work both together can do in one hour = 1/6+1/4 = 5/12

so the first man did 2/6 or 1/3 work in 2 hours till the second came

so work remaining = 2/3

so time needed to compelete the work = (2/3) / (5/12) = 2/3 * 12/5 = 8/5 hours

so 1 and 3/5 hours is needed to compelete the work