Proportions

Converting Customary Units Using Proportions

Proportion: a balanced

equation that shows the relationship among various quantities.

Fractions with equal cross products

Vocabulary

Same labels go on the same line 1st fraction contains the conversion

key 2nd fraction contains information

from the problem From key From problem

1 pound = 4 pounds 16 ounces x ounces

Helpful hints to convert with proportions

Conversion Key: 1 pound = 16 ounces

1 ton = 2,000 pounds

1. A box weighs 32 oz. How many pounds is that?

From key From problemProportion:

= Cross products: 16(x) = 32(1)

Guided Practice

1 pound16 ounces

X pounds32 ounces

CHECK FOR REASONABLENESS

Small to large unit = smaller answer

Check

Conversion Key: 1 pound = 16 ounces 1 ton = 2,000 pounds

2. A bag of rice weighs 60 oz. How many pounds is that?

From key From problemProportion: =

Cross products: 16(x) = 60(1)

Guided Practice

1 pound16 ounces

X pounds60 ounces

CHECK FOR REASONABLENESS

Small to large unit = smaller answer

Check

A monkey weighs 13 pounds.

How many ounces is that?

The SWAT team van weighs 6 tons. How many pound is that?

Try on your own

1st fraction: conversion chart 2nd fraction: info in problem Calculate cross products and

solve for variable Check for reasonableness

Independent Practice