Discussion

Explanation:

Work done by Amit in one day = $\frac{1}{12}$
Work done by Sagar in one day = $\frac{1}{15}$

In one day, Amit and Sagar can do = $\frac{1}{12}$ + $\frac{1}{15}$ = $\frac{3}{20}$^th

Hence, in 4 days they will complete $4\times \frac{3}{20}$ = $\frac{3}{5}$^th of the work.

Hence, amount of work remaining after 4 days = 1 - $\frac{3}{5}$ = $\frac{2}{5}$.

Hence, option (c).
 

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