CPM time–cost trade-off: formula used to determine an activity’s cost slope In Critical Path Method (CPM) crashing, each activity has normal/crash time and cost data. Select the correct expression for the cost slope used to guide crashing decisions.

Given/Definition
Cost slope measures the incremental cost per unit time saved when crashing an activity.

Correct formula
Cost slope = (Crash cost − Normal cost) ÷ (Normal time − Crash time)

Step-by-step rationale
• Numerator: extra cost you pay to crash = Crash cost − Normal cost.• Denominator: time saved by crashing = Normal time − Crash time.• Therefore, slope gives cost per day (or per week) saved, which you compare across activities to crash most economically.

Verification example
If normal time = 10 days, crash time = 7 days (save 3 days); normal cost = ₹40,000, crash cost = ₹55,000 (extra ₹15,000).Cost slope = 15,000 ÷ 3 = ₹5,000 per day saved.

Common pitfall
Do not invert the time difference; the denominator must be time saved (Normal − Crash).

Final Answer
(Crash cost − Normal cost) ÷ (Normal time − Crash time).