Question

An aluminum bar 3 feet long weighs 12 pounds. What is the weight of a similar bar that is 3 feet 4 inches long?

Answer 1

Answer: 13
`(1)/(3)` pounds

Explanation:

We will set up a proportion. I will have the weight, in pounds, on the top (numerator) and the length, in inches, on the bottom (denominator).

`(12)/(36) =(x)/(40)`

Cross-multiply:

36 * x = 12 * 40

36x = 480

Divide both sides of the equation by 36:

x = 13
`(1)/(3)` pounds

Answer 2

Explanation:

First find unit weight.

1 foot = 12 inches

3 ft = 3*12 = 36 inches

3ft 4 inches = 36 + 4 = 40inches

Weight of 36 inches long bar = 12 pounds

Weight of 1 inch bar = 12/36

`\text{Weight of 40 inches long bar = $(12)/(36)*40$}`

= 13.3 pounds