Question

A can do a piece of work in 12 days and B can do the same work in 20 days they work together for three days and then A goes away in how many days will B finish the work?

Answer 1

Answer:

Let a complete work be as 1.

A complete work in 25 days,

So in 1 day, A do work = 1/25

B complete work in 20 days,

So in 1 day, B do work = 1/20

In 5 days both do work = 5*(1/25)+5*(1/20) = 1/5+1/4 = 9/20

So 9/20 work is completed in 5 days.

Now, remaining work=1–9/20 = 11/20

So B will complete work in = (11/20)/(1/20)=11 days

Answer 2

Your Answer:

Given:-

• A can finish work in 12 days
• B can finish same work in 20 days

Solution:-

Work done by A and B in 3 days

$\large \tt 3(\frac{1}{12}+\frac{1}{20})\\\\=3(\frac{5+3}{60})\\\\=3(\frac{8}{60})\\\\=\frac{8}{20}\\\\=\frac{2}{5}$

Remaining part of work

$\large \tt 1-\frac{2}{5}\\\\=\frac{5-2}{5}\\\\=\frac{3}{5}$

Now time taken by B to complete the remaining work

$\large \tt \frac{3}{5}\times20\\\\=12 \:days$

So, the answer is 12 days