Map scale 1 cm : 20 km, 90 km in real life

Step by step, with the reason for every step · Scale drawings and maps · Geometry

Step by step

Question: with the scale 1 cm : 20 km, how long is 90 km in real life on the map?

map → real

The scale means: 1 cm on the map is 20 km for real.

1 cm → 20 km

90 km is how many times 20 km?

90 divided by 20 is 4.5.

90 ÷ 20 = 4.5

So it is 4.5 times the scale.

The map length is 4.5 times 1 cm too.

4.5 × 1 cm → 90 km

So on the map it is 4.5 cm.

4.5 cm → 90 km

Let's check: go back.

4.5 times 20 should give the real length, 90.

4.5 × 20 = 90

We get it again.

So 4.5 cm is right!

Let's look back.

First: how many times.

Last: check.

Answer

4.5 cm → 90 km

Try this one yourself, then check:

Scale 1 cm : 16 km. 88 km in real life: on the map?

Show the answer

5.5 cm