Question

Zinc has a density of 0.258 lb/in³ (pounds per cubic inch).

Darius is making a pyramid out of solid zinc. The pyramid has a square base 6 inches on each side, and a height of 2.5 inches.

How many pounds of zinc does he need?

Show all your work. Do not round the final answer.

Answer 1

For this case we have that by definition the mass is given by:

$m = D * V$

Where,

• D: density
• V: Volume

The volume of a pyramid is given by:

$V = \frac {1} {3} * A * h$

Where,

• A: area of ​​the base
• h: height

Substituting values ​​we have:

$V = \frac {1} {3} * (36) * (2.5)\\V = 30$

We now calculate the mass:

$m = (0.258) (30)\\m = 7.74\ lb$

Answer:

he needs 7.74 pounds of zinc