Cost Slope :- The term 'cost-slope' is defined as the “increase in the cost of the activity per unit decrease in the time”.

$$Cost\ slope\ =\ Crash\ cost\ C_c\ –\ \frac{Normal\ cost\ N_c}{Normal\ time\ N_{tt}}$$

Cost slope is defined as the ratio of difference between Crash cost & Normal cost and difference between Normal Time & Crash Time.

Crash Time is time taken by the activity when additional resources, overtime and other special measures are taken to speed up (crash) the activity.