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P completed 25\frac{2}{5} part of certain work in 12 days. Further, Q completed the rest of the work in 18 days. In how many days could P and Q complete the work, if they worked together?

Solution

✅ Correct Option: 4

P completed 25\frac{2}{5} of the work in 12 days.

Q completed the remaining part.

Remaining work =1−25=35= 1 - \frac{2}{5} = \frac{3}{5}

Q completed 35\frac{3}{5} of the work in 18 days.


P's work rate per day:

=2/512= \frac{2/5}{12}

=25×112= \frac{2}{5} \times \frac{1}{12}

=260= \frac{2}{60}

=130= \frac{1}{30} of the work per day

P alone can complete the entire work in 30 days.


Q's work rate per day:

=3/518= \frac{3/5}{18}

=35×118= \frac{3}{5} \times \frac{1}{18}

=390= \frac{3}{90}

=130= \frac{1}{30} of the work per day

Q alone can complete the entire work in 30 days.


Combined work rate when P and Q work together:

=130+130= \frac{1}{30} + \frac{1}{30}

=230= \frac{2}{30}

=115= \frac{1}{15} of the work per day


Days needed to complete the work together:

=1115= \frac{1}{\frac{1}{15}}

=1×15= 1 \times 15

=15= 15 days

Therefore, P and Q working together can complete the work in 15 days.

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