### Question: Swapnil can build a sofa in 16 days. Working together with Revathi he can finish the work in 129/17 days. Find the number of days taken by Revathi to complete the work if she works alone.

- 128/17 days
- 128/16 days
- 6 days
- 128/9 days

Answer: 4. 128/9 days

Solution:

building a sofa workdone = w

Swapnil can do in 16 days = w=16s

s=speed of swapnil

equation working together

(s+r)128/17=16s

r=(16s(17))/128 -s

r=1.125 s ( substituting s)

r=1.125 w/16

r (16)/1.125= w

r(14.22)=w

rt=w

t=128/9 days