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81 equally efficient people could complete a piece of work in 15 days. Initially 45 such people started working together. But after they worked together for 6 days their employer wanted that the work should be completed in a total of 21 days. However any new worker who joins is only 60%60\% as efficient as any of the 45 people already working. How many new workers did the employer hire to work alongside the initial 45 people to meet the deadline?

Solution

✅ Correct Option: 1

Total work =81×15=1215= 81 \times 15 = 1215 units (1 unit == work of one original person in one day).


Work done by 4545 people in 66 days =45×6=270= 45 \times 6 = 270 units

Remaining work =1215−270=945= 1215 - 270 = 945 units

The deadline of 2121 days includes the first 66 days, so days left =21−6=15= 21 - 6 = 15


Work needed per day =94515=63= \dfrac{945}{15} = 63 units

The original 4545 people do 4545 units per day.

Extra work needed per day =63−45=18= 63 - 45 = 18 units


Each new worker is 60%60\% as efficient, so does 0.60.6 unit per day.

Number of new workers =180.6= \dfrac{18}{0.6}

=30= 30

Therefore, the employer hired 3030 new workers.

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