Lesson 5.2 · Measurement
Centimeters and meters
Most of the world measures length in centimeters and meters. These are called metric units. You measure with them the same way you measure with inches.
Centimeters
A centimeter is a very small unit. Your fingertip is about 1 centimeter wide. We write cm for short.
Many rulers have inches on one side and centimeters on the other. Line up the end of the object with 0. Then read the number at the other end.
A ruler in centimeters. The eraser starts at 0 and ends at 7.
The eraser is 7 cm long.
Meters
A meter is 100 centimeters. We write m for short. A meter stick is 1 meter long. A door is about 2 meters tall.
Metric units of length
1 meter = 100 centimeters
Use centimeters for small things. Use meters for big things, like a room or a hallway.
A meter is a little longer than a yard.
Worked example: Read the ruler
A leaf lines up with 0. Its tip is at the 9 mark. How long is the leaf?
It goes from 0 to 9. The leaf is 9 cm long.
Worked example: Not starting at 0
A straw starts at the 3 mark and ends at the 10 mark. How long is it?
Count the spaces from 3 to 10. That is 7 spaces. You can also subtract: . The straw is 7 cm long.
Worked example: Pick the unit
Is a swimming pool 25 cm long or 25 m long?
25 cm is shorter than a ruler and a half. A pool is much longer than that. The pool is 25 m long.
Common mistake
Count the spaces between marks, not the marks. From 3 to 10 there are 8 marks but only 7 spaces.
Practice
A crayon lines up with 0. Its other end is at the 6 mark. How many centimeters long is it?
A ruler in centimeters
Type a number.
How many centimeters are in 1 meter?
Type a number.
Which unit is best for measuring the length of a hallway?
A bead string starts at the 4 mark and ends at the 9 mark. How many centimeters long is it?
The string does not start at 0.
Type a number.
About how long is a new pencil?
A rope is 2 meters long. How many centimeters long is it?
Type a number.
Leo measured a bench in meters and in centimeters. Which number did he get in centimeters?