Step by step
The question
Question: with the scale 1 cm : 3 m, how long is 5 cm on the drawing for real?
drawing → real
The scale means: 1 cm on the drawing is 3 m for real.
1 cm → 3 m
1 Multiply both sides
On the drawing we have 5 cm.
That is 5 times 1 cm.
So the real length is 5 times 3 m too.
5 cm → 3 × 5 m
We multiply both sides by the same number, 5.
× 5 on both sides
3 times 5 is 15.
So the real length is 15 m.
5 cm → 15 m
2 Check
Let's check: go back.
15 divided by 3 should give the drawing length, 5.
15 ÷ 3 = 5
We get it again.
So 15 m is right!
Let's look back.
First: multiply both sides.
Last: check.
Answer
5 cm → 15 m