When you have two things, you often ask "which is longer?" or "by how much do they differ?".
To answer that, you have to measure them first.
Which is longer — compare numbers
How to do it:
- Measure the first thing.
- Measure the second.
- Compare the numbers.
Example: Pen A = 14 cm, Pen B = 18 cm.
14 < 18 → Pen B is longer.
By how much — subtract
We often want the difference:
Longer − shorter = difference.
For Pen A (14 cm) and Pen B (18 cm):
Pen B is 4 cm longer.18 − 14 = 4.
Example with the same unit
Ribbon A = 50 cm, ribbon B = 75 cm.
75 − 50 = 25 cm.
Ribbon B is 25 cm longer.
Watch out: same unit
When comparing, both things must be in the same unit!
Pen = 15 cm. Table = 1 m.
I cannot compare 15 and 1 — that would be wrong.
First convert: 1 m = 100 cm.100 − 15 = 85 cm.
The table is 85 cm longer than the pen.
Trick: line them up
If you don't have a ruler, you can compare lengths physically:
- Put the starts of the things on the same line.
- See which one sticks out further.
For pencils, for example: line them up at the points and see which one is longer.
Summary
- Longer / shorter = compare the numbers.
- By how much they differ = longer − shorter.
- Before comparing, both must be in the same unit.
- Quick comparison: line up the starts side by side.