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# Measurement for Praxis I: Pre-Professional Skills Test Study Guide (page 3)

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Updated on Jul 5, 2011

2. Simplify the answer by converting smaller units into larger units when possible.
3. ##### Example

Add 4 pounds 5 ounces to 20 ounces.

Be sure to add ounces to ounces.

Because 25 ounces is more than 16 ounces (1 pound), simplify by dividing by 16:

Then add the 1 pound to the 4 pounds:

4 pounds 25 ounces = 4 pounds + 1 pound 9 ounces = 5 pounds 9 ounces

#### Subtraction with Measurements

1. Subtract like units if possible.
2. If not, regroup units to allow for subtraction.
3. Write the answer in simplest form.
4. For example, 6 pounds 2 ounces subtracted from 9 pounds 10 ounces.

Subtract ounces from ounces.

Then subtract pounds from pounds.

Sometimes, it is necessary to regroup units when subtracting.

##### Example

Subtract 3 yards 2 feet from 5 yards 1 foot.

Because 2 feet cannot be taken from 1 foot, regroup 1 yard from the 5 yards and convert the 1 yard to 3 feet. Add 3 feet to 1 foot. Then subtract feet from feet and yards from yards:

Therefore, 5 yards 1 foot – 3 yards 2 feet = 1 yard 2 feet.

#### Multiplication with Measurements

1. Multiply like units if units are involved.
3. ##### Example

Multiply 5 feet 7 inches by 3.

Multiply 7 inches by 3, then multiply 5 feet by 3. Keep the units separate.

Because 12 inches = 1 foot, simplify 21 inches.

15 ft. 21 in. = 15 ft. + 1 ft. 9 in. = 16 ft. 9 in.

##### Example

Multiply 9 feet by 4 yards.

First, decide on a common unit: either change the 9 feet to yards, or change the 4 yards to feet. Both options are explained below:

Option 1:

To change yards to feet, multiply the number of feet in a yard (3) by the number of yards in this problem (4).

3 feet in a yard · 4 yards = 12 feet

Then multiply: 9 feet × 12 feet = 108 square feet.

(Note: feet · feet = square feet = ft.2)

Option 2:

To change feet to yards, divide the number of feet given (9), by the number of feet in a yard (3).

9 feet ÷ 3 feet in a yard = 3 yards

Then multiply 3 yards by 4 yards = 12 square yards.

(Note: yards × yards = square yards = yd.2)