Question

A is thrice as good as workman as B and therefore is able to finish a job in 60 days less than B. Working together, they can do it in:

• A. 20 days
• B. days
• C. 25 days
• D. 30 days

Answer 1

The correct option is B days

Ratio of times taken by A and B = 1 : 3.
The time difference is (3 - 1) 2 days while B take 3 days and A takes 1 day.
If difference of time is 2 days, B takes 3 days.
If difference of time is 60 days,
B takes \left(\frac32\times60\right)=90 days
So, A takes 30 days to do the work.
A’s 1 day’s work $=\frac{1}{30}$
B’s 1 day’s work $\frac{1}{90}$
(A+B’s 1 day’s work $=(\frac{1}{30}+\frac{1}{90})=\frac{4}{90}=\frac{2}{45}$
$\therefore$ A and B together can do the work in $\frac{45}{2}=22\frac{1}{2}$days.