A block of ice had a volume of 1,000 cubic inches when it started melting. 18 minutes later, the volume was 591 cubic inches. What was the average rate of change of the volume in cubic inches per minute? Round to the nearest hundredth.

Average rate of change of volume = (change in volume) / (time for the change)

Change in volume = (591 in³ - 1,000 in³) = - 409 in³

Time for the change = 18 minutes

Average rate of change of volume = (-409 in³) / (18 min) = - 22.722 ... in³ per minute

Rounded to the nearest hundredth, that's - 22.72 in³ per minute.