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Ram can do a piece of work in 10 days and Anshu in 20 days. They work together but 2 days before the completion of the work, Ram leaves and Anshu completes the work. In total how many days was the work completed?

Solution

✅ Correct Option: 3

Ram's work rate = 110\dfrac{1}{10} of the work per day

Anshu's work rate = 120\dfrac{1}{20} of the work per day

Combined rate when working together:

110+120\dfrac{1}{10} + \dfrac{1}{20}

=220+120= \dfrac{2}{20} + \dfrac{1}{20}

=320= \dfrac{3}{20} of the work per day


Let the total time taken = xx days

For (x−2)(x - 2) days: Both Ram and Anshu work together

For the last 2 days: Only Anshu works alone


Work done by both together = (x−2)×320(x - 2) \times \dfrac{3}{20}

Work done by Anshu alone = 2×1202 \times \dfrac{1}{20}

=220= \dfrac{2}{20}

=110= \dfrac{1}{10}

Total work must equal 1:

(x−2)×320+110=1(x - 2) \times \dfrac{3}{20} + \dfrac{1}{10} = 1


(x−2)×320=1−110(x - 2) \times \dfrac{3}{20} = 1 - \dfrac{1}{10}

(x−2)×320=910(x - 2) \times \dfrac{3}{20} = \dfrac{9}{10}

x−2=910×203x - 2 = \dfrac{9}{10} \times \dfrac{20}{3}

x−2=18030x - 2 = \dfrac{180}{30}

x−2=6x - 2 = 6

x=8x = 8 days


Therefore, the work was completed in 8 days.

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