Work Efficiency — Revision Notes

⚡ 30-Second Revision

Rate = work ÷ time.
Add rates, not completion times.
Time ratios invert efficiency ratios.
Split the timeline when workers change.
Remaining work determines the later interval.

2-Minute Revision

Represent each worker's contribution in the same work units per day or hour. Add independent positive rates, subtract a stipulated opposing rate and multiply by time to find completed work. A change in team creates a new interval. An efficiency increase of 25% means a time multiplier of 1/1.25, or 0.8, for the same job. Check whether the answer asks for additional time or the full elapsed duration.

5-Minute Revision

A completes a job in 15 days and B in 10 days. Choose 30 units, so their rates are 2 and 3 units daily. Together for four days they complete 20 units. If A then leaves, B needs 10/3 more days. Total elapsed time is 22/3 days. Explain why 10/3 and 22/3 are both meaningful but answer different questions. Check the work: 4 × 5 + (10/3) × 3 = 30.

Vyyuha Quick Recall

R-T-W: Rate × Time = Work. Recalculate the rate whenever the team changes.