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Illustrations · Q9

Q.For a job with Time Allowed = 10 hours and Time Rate = ₹20 per hour, compute the Rowan Bonus for Time Taken = 3, 4, 5, 6 and 7 hours, and show that the Bonus is at its maximum when Time Taken equals exactly half of the Time Allowed.

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Bonus = (Time Saved ÷ Time Allowed) × Time Taken × Time Rate, with Time Allowed = 10 hours and Time Rate = ₹20, computed for each Time Taken value:

Time Taken (hrs)Time Saved (hrs)Time-Saved RatioBonus (₹)
370.700.70 × 3 × 20 = 42
460.600.60 × 4 × 20 = 48
550.500.50 × 5 × 20 = 50
640.400.40 × 6 × 20 = 48
730.300.30 × 7 × 20 = 42

The Bonus rises steadily as Time Taken falls from 3 to 5 hours (₹42 → ₹48 → ₹50), then FALLS by the exact mirror-image amounts as Time Taken keeps falling further, from 5 to 7 hours (₹50 → ₹48 → ₹42). The maximum, ₹50, occurs precisely at Time Taken = 5 hours — exactly half of the 10-hour Time Allowed (i.e., exactly 50% of the time has been saved) — and the table is perfectly symmetric around that point (Time Taken = 4 and 6 hours both give ₹48; Time Taken = 3 and 7 hours both give ₹42). This confirms, with real figures, the self-limiting property stated in Section 4.B: saving MORE …

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