Exercise 19 Page 251

We have a concrete forming tube with a volume

V,

where

V

is the product of its length

ℓ

and the area

A

of its circular base.

V = ℓ \cdot A_{base}

We are told that we can make

\frac{2}{3} ft^{3}

of cement per bag. We need to write a rule to find number of bags of cement needed to fill a tube with

ℓ = 4

feet and with either

r = 4

inches,

r = 5

inches, or

r = 6

inches.

Since the volume

V

of a tube is the product of its length

ℓ

and the area

A

of its circular base with radius

r,

we can write a rule as follows.