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Ratio of 3 m to 50 cm

Step by step, with the reason for every step · Ratios with units · Foundations

Step by step

The question

Question: write the ratio of 3 meters to 50 centimeters in its simplest form.

3 m : 50 cm

Careful!

The units are not the same: meters and centimeters.

3 to 50 would compare different things.

Careful: not 3 : 50 ✗

1 Same units

A ratio only compares amounts in the same unit.

We change to the smaller unit, centimeters, so there are no fractions.

1 meter is 100 centimeters.

1 m = 100 cm

So 3 meters is 3 times 100: 300 centimeters.

= 3 m = 3 × 100 cm = 300 cm

2 Drop the units

Now the ratio is 300 centimeters to 50 centimeters.

= 300 cm : 50 cm

Both are in centimeters.

The same units cancel, so we cross them out.

That leaves 300 to 50.

= 300 : 50

3 Simplify

300 and 50 can both be divided by 50.

We divide both parts by 50.

The ratio stays the same.

= 300 ÷ 50 : 50 ÷ 50

300 divided by 50 is 6.

50 divided by 50 is 1.

So the ratio is 6 to 1.

= 6 : 1

4 Check

Let's check: times each part by 50.

We get 300 centimeters and 50 centimeters again.

6 × 50 = 300 cm, 1 × 50 = 50 cm

And 300 centimeters divided by 100 is 3 meters, as in the question.

So the answer is right!

300 cm = 300 ÷ 100 = 3 m

Let's look back.

First: same units.

Then: drop the units.

Then: simplify.

Last: check.

Answer
= 6 : 1

Your turn

Try this one yourself, then check:

Write the ratio of 6 m : 50 cm
Show the answer
12 : 1

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