Lesson 5.1 · Measurement
Inches, feet and yards
Paper clips and cubes come in different sizes. So people agreed on units that are always the same: inches, feet and yards. A ruler helps you measure with them.
Inches
An inch is a short unit. A paper clip is about 1 inch long. A ruler shows inches with numbers.
To measure, line up one end of the object with the 0 mark. Then read the number at the other end.
A ruler in inches. The crayon starts at 0 and ends at 4.
The crayon is 4 inches long.
Feet and yards
A foot is 12 inches. A school ruler is 1 foot long.
A yard is 3 feet. A yardstick is 1 yard long. That is about as long as a big step.
Customary units of length
- 1 foot = 12 inches
- 1 yard = 3 feet
Use inches for small things, feet for bigger things, and yards for long things.
Worked example: Read the ruler
A key lines up with the 0 mark. Its other end is at the 3 mark. How long is the key?
The key starts at 0 and ends at 3. It is 3 inches long.
Worked example: Pick the unit
Would you measure a soccer field in inches or yards?
A soccer field is very long. Inches are tiny, so you would need a huge number of them. Use yards.
Big units, small units
A desk is 2 feet long. That is the same as 24 inches, because 12 + 12 = 24.
The desk did not change. When the unit is bigger, you need fewer of them.
Worked example: Same length, two units
A rug is 2 yards long. How many feet is that?
Each yard is 3 feet. So 2 yards is 3 + 3 = 6 feet.
Common mistake
Start at 0, not at 1. If you start at 1, your answer will be 1 inch too big.
Practice
A pencil lines up with the 0 mark. Its other end is at the 5 mark. How many inches long is the pencil?
A ruler in inches
Type a number.
How many inches are in 1 foot?
Type a number.
How many feet are in 1 yard?
Type a number.
Which unit is best for measuring a bug?
A spoon starts at the 2 mark and ends at the 5 mark on a ruler. How many inches long is the spoon?
The spoon does not start at 0.
Type a number.
Mia measured a table in feet and in inches. Which is true?
A path is 3 yards long. How many feet long is it?
Type a number.