Discussion

Question:

A can do a work in 20 days and B in 40 days. If they work on it together for 5 days. Then fraction of the work that is left, is:

Explanation:

Fraction of work done in 5 days = $(\frac{1}{20} + \frac{1}{40})$ × 5 = $\frac{3}{40}$ × 5 = $\frac{3}{8}$ ^th.

∴ Fraction of work left = 1 – $\frac{3}{8}$ = $\frac{5}{8}$

Hence, option (a).

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