The volume of a right circular cylinder is

.

To find the volume before Mr. Thorpe climbs into the pool, plug in r = 1.5 m and h = 0.7 m. I'll call this V1:

.

To find the volume after Mr. Thorpe submerges in the pool, plug in r = 1.5 m and h = 0.72 m. I'll call this V2:

.

To find Mr. Thorpe's volume, subtract the two volumes:

Can you finish?