1. Vocabulary
customary system

2. Customary Units of Length
If you do not have an instrument, such as a ruler, scale, or measuring cup, you can estimate the length, weight, and capacity of an object by using a benchmark.
The customary system is the measurement system often used in the United States. It includes units of measurement for length, weight, and capacity.
Customary Units of Length
Unit
Abbreviation
Benchmark
Inch
in.
Width of your thumb
Foot ft
Distance from your elbow to your wrist
Yard yd
Width of a classroom door
mile mi
Total length of 18 football fields

3. Additional Example 1: Choosing Appropriate Units of Length
What unit of measure provides the best estimate? Justify your answer.
A. A doorway is about 7 _____ high.
B. A calculator is about 6 _____ long.
Think: The height of a doorway is about 7 times the distance from your elbow to your wrist.
A doorway is about 7 ft high.
Think: The length of a calculator is about 6 times the width of your thumb.
A calculator is about 6 in. long.

4. Check It Out: Example 1
What unit of measure provides the best estimate? Justify your answer.
A. A 4-door sedan is about 5 _____ long.
B. A students desk is about 3 _____ long.
Think: The length of a sedan is about 5 times the width of a classroom door.
A 4-door sedan is about 8 yd long.
Think: The length of a students desk is about 3 times the distance from your elbow to your wrist.
A students desk is about 4 ft long.

5. Customary Units of Weight
Abbreviation
Benchmark
Ounce oz
A slice of bread
Pound lb
A loaf of bread
Ton T
A small car

6. Additional Example 2: Choosing Appropriate Units of Weight
What unit of measure provides the best estimate? Justify your answer.
A. A loaf of bread weighs about 16 _____ .
B. A bike could weigh 20 _____ .
Think: A loaf of bread has a weight of about 16 slices of bread.
A loaf of bread weighs about 16 oz.
Think: A bike could have a weight of about 20 loaves of bread.
A bike could weigh 20 lbs.

7. Check It Out: Example 2
What unit of measure provides the best estimate? Justify your answer.
A. A black rhino could weigh about 1 _____ .
B. A DVD remote control weighs about 8 ____ .
Think: A black rhino has a weight of about a small car.
A black rhino can weigh about 1 T.
Think: A DVD remote control has a weight of about 8 slices of bread .
A DVD remote control weighs about 8 oz.

8. Customary Units of Capacity
Capacity deals with volume, or the amount a container can hold.
Customary Units of Capacity
Unit
Abbreviation
Benchmark
Fluid ounce
fl oz
A spoonful
Cup c
A glass of juice
Pint pt
A small bottle of salad dressing
Quart qt
A small container of paint
Gallon
gal
A large container of milk

9. Additional Example 3: Choosing Appropriate Units of Capacity
What unit of measure provides the best estimate? Justify your answer.
A large water cooler holds about 10 _____ t of water.
Think: A large water cooler holds 10 times the amount of a large container of milk.
A large water cooler holds about 10 gal of water.

10. Check It Out: Example 3
What unit of measure provides the best estimate? Justify your answer.
A small fish aquarium holds about 20 _____ t of water.
Think: A small fish aquarium holds 20 times the amount of a small container of paint.
A small fish aquarium holds about 20 qt of water.

11. Additional Example 4: Estimating Measurements
Estimate the length of the line segment to the nearest half, fourth, or eighth of an inch.
The line segment is closest to 1 in.
5 8
The length of the line segment is about 1 in.
5 8

12. The line segment is between 1 and 1 in. 1 4 3 8
Check It Out: Example 4
Estimate the length of the line segment to the nearest half, fourth, or eighth of an inch.
The line segment is between 1 and 1 in.
1 4
3 8
The length of the line segment is closest to 1 in.
1 4

13. What unit of measure provides the best estimate?
Lesson Quiz
What unit of measure provides the best estimate?
1. A row boat is 10 _____ long.
2. A skateboard is 30 _____ long.
3. A pair or earphones weighs 4 _____.
4. Drinking water is delivered in 5 _____ bottle.
5. Estimate the length of the line segment to the nearest half, fourth, or eighth of an inch. ft
in. oz
gal
2 in.