Question

20 ants can complete a piece of work in 30 days and 30 spiders can complete the same work in 24 days. If all 20 ants and 30 spiders work together, in how many days will the work get completed?

• A. 12 days
• B.
• C.
• D. 20 days
• E. None of these

Answer 1

The correct option is C

20 ant's 1 day's work $=\frac{1}{30}$; 30 spider's 1 day's work $=\frac{1}{24}$
(20 ant + 30 spider)'s 1 day's work $=(\frac{1}{30}+\frac{1}{24})=\frac{9}{120}=\frac{3}{40}$
$\therefore$ 20 ants and 30 spiders will complete the work in $\frac{3}{40}=13\frac{1}{3}days$