The base of pyramid a is a rectangle with a length of 10 meters and a width of 20 meters. the base of pyramid b is a square with 10-meter sides. the heights of the pyramids are the same.
the volume of pyramid a is the volume of pyramid b. if the height of pyramid b increases to twice that of pyramid a, the new volume of pyramid b is the volume of pyramid a.

Given:
Pyramid A: Base is rectangle with length of 10 meters and width of 20 meters.
Pyramid B: Base is square with 10 meter sides.
Heights are the same.

Volume of rectangular pyramid = (L * W * H) / 3
Volume of square pyramid = a² * h/3

Let us assume that the height is 10 meters.
V of rectangular pyramid = (10m * 20m * 10m)/3 = 2000/3 = 666.67 m³
V of square pyramid = (10m)² * 10/3 = 100m² * 3.33 = 333.33 m³

The volume of pyramid A is TWICE the volume of pyramid B.

If the height of pyramid B increases to twice the of pyramid A, (from 10m to 20m),  

V of square pyramid = (10m)² * (10*2)/3 = 100m² * 20m/3 = 100m² * 6.67m = 666.67 m³

The new volume of pyramid B is EQUAL to the volume of pyramid A

B. 2 1/2 feet. multiply 2.5 inches by 12 to get thirty inches then divide by 12 to get 2.5 feet