a solid pyramid with a square base with side 12 cm and height 25 cm is made of metal. The metal is melted to form spherical ball bearings of radius 7 mm. How many pyramids are needed to form 2490 ball bearings?

3 pyramids.

Step-by-step explanation:

The volume of one pyramid is 1/3 * b^2 * h

= 1/3 * 12^2 * 25

= 1200 cm^3.

The volume of one ball bearing = 4/3 * π * 0.7^3

= 1.43676 cm^3.

Therefore the volume of 2490 ball bearings = 2490 * 1 .43676

= 3577.53 cm^3.

So we need 3577.53 / 1200 = 2.98 = 3 pyramids.

4

step-by-step explanation: