Two objects can both be measured. The question is how much longer one is.
Step 1: Let's Learn
Read it, or press Listen and follow the words.
Take the smaller from the bigger
A 12 cm pen and an 8 cm crayon. 12 − 8 = 4, so the pen is 4 cm longer.
The answer keeps the unit
The difference is a length too. It is 4 centimetres, not just 4.
How much longer is a subtraction
To find how much longer one thing is than another, subtract the shorter length from the longer one. A 17 cm ribbon and a 9 cm ribbon differ by 17 - 9 = 8 cm. The answer is not a length of any object in the problem — it is the gap between them.
Why lining them up shows it
Put the two ribbons side by side with their left ends together. The extra piece sticking out at the right end is the difference. That sticking-out piece is what the subtraction calculates. Drawing it this way makes the subtraction feel obvious rather than a rule to remember.
Both lengths must use the same unit
You cannot subtract 9 centimetres from 2 metres directly. Change the metres to centimetres first: 2 metres is 200 centimetres, so the difference is 200 - 9 = 191 centimetres. Comparing quantities always means putting them in the same unit first.
Step 2: Try It Yourself
Tap and try it out.
Pen (cm)
12
Crayon (cm)
8
4
12 is 4 more than 8.
Step 3: Watch an Example
One step at a time.
Watch Leo Compare
Leo measures a pen at 12 cm and a crayon at 8 cm.
- Step 1
He lines both up at the same starting line.
Step 4: Your Turn
Practice makes it stick.
Two Ribbons
Problem 1 of 2
A red ribbon is 15 cm and a blue one is 9 cm. How much longer is the red one?
cm
Two Sticks
Problem 2 of 2
A stick is 18 cm. Another is 18 cm. How much longer is the first?
cm
Find the Difference
1 of 3
14 cm and 6 cm. How much longer is the first?
2 of 3
20 cm and 13 cm. How much longer is the first?
3 of 3
9 inches and 12 inches. How much shorter is the first?
Step 5: Quick Check
Show what you know.
Question 1 of 2
A 16 cm rope and an 11 cm rope. How much longer is the first?
Question 2 of 2
What unit does the difference have?
What You Learned
- To compare, measure both and subtract.
- The difference is how much longer one is.
- The answer keeps the unit.