One object can be measured in two units. The object does not change.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
But the numbers do
A pencil might be 15 centimetres and about 6 inches. Both are true.
Smaller unit, bigger number
Centimetres are smaller, so it takes more of them to cover the same length.
Always say the unit
A number on its own says nothing. "15" could be long or short until you say what.
The rule, and why it is true
Measure one object twice with two different units and the smaller unit always gives the bigger number. If your units are small, it takes more of them to cover the same distance. A table that is 1 metre long is 100 centimetres long: same table, smaller unit, bigger number.
Predict before you measure
This rule lets you predict. Before measuring a desk in inches when you already know it is 60 centimetres, ask yourself: is an inch bigger or smaller than a centimetre? An inch is bigger, so the number of inches must be smaller than 60. If you measure and get 150, something went wrong.
A number without a unit means nothing
Saying a rope is "8" tells no one anything. Eight what? Eight centimetres is shorter than your hand; eight metres crosses a room. Always write the unit next to the number. This habit matters more and more as the maths gets harder.
Step 2: Try It Yourself
One object, two scales. Compare the two readings.
centimetres
05101520
inches
05
It starts at 0 and ends at 10, so it is 10 centimetres long.
The same object is about 3.9 inches. Inches are bigger, so it takes fewer of them.
Step 3: Watch an Example
One step at a time.
Watch Leo Measure Twice
Leo measures the same crayon in centimetres and then in inches.
- Step 1
In centimetres it reads 10.
Step 4: Your Turn
Practice makes it stick.
Two Answers
Problem 1 of 2
A stick is measured in centimetres and in metres. Which number is bigger?
A Missing Word
Problem 2 of 2
Ana says her ribbon is "12". Why is that not an answer?
Bigger Unit or Bigger Number?
1 of 3
You measure a desk in inches, then in feet. Which number is bigger?
2 of 3
If you swap to a bigger unit, does the number go up or down?
3 of 3
A desk is 3 feet long. How many inches is that?
Step 5: Quick Check
Show what you know.
Question 1 of 2
Which gives the bigger number, centimetres or metres?
Question 2 of 2
Why must you say which unit you used?
What You Learned
- One object can be measured in different units.
- A smaller unit gives a bigger number.
- Always say the unit with the number.