Question

A and b takes 6 hours and 9 hours respectively to conpletr a work. a work for 1 hour and then b works for two hours how much work is done in these 3 hours

Answer 1

In A complete 1 work in 6 h
B complete 1 work in 9 h
If A work 1 h=1/6 work done
B work 2 h=2/9 work done
Total work =1/6+2/9
7/18

Answer 2

7/8 of total work is done in these 3 hours.

Step-by-step explanation:

Given:

Here A and B take 6 hours and 9 hours respectively to complete a work, we get

A can do a piece of work in 6 hours,

So, A can do a piece of work in 1 hour = $\frac{1}{6}$ of work       [1]

And  B can do the same work in 9 hours,

So, B can do a piece of work in 1 hour = $\frac{1}{9}$ of work,

Then,

B can do a piece of work in 2 hours = $\frac{1}{9}\times 2 = \frac{2}{9}$ of work      [2]

Therefore, from eq 1 and 2

Work is done in these 3 hours = $\frac{1}{6}+ \frac{2}{9}$

                                                   = $\frac{9+6\times2}{6\times9}$

                                                   = $\frac{9+12}{54}$

                                                   = $\frac{21}{54}$

                                                  = $\frac{7}{18}$ of total work    

$\frac{7}{18}$ of total work is done in these 3 hours.