Density 0.8 g/cm³, volume 20 cm³, find the mass Step by Step

Step by step

The question

Question: find the mass when the density is 0.8 g/cm³ and the volume is 20 cm³.

Density 0.8 g/cm³, volume 20 cm³. Find the mass.

1 Write the rule

The rule: density is the mass divided by the volume.

density = massvolume

Density tells us how much mass there is in 1 cm³.

So its unit is g per cm³.

density = the mass of 1 cm³

unit: g ÷ cm³ → g/cm³

2 Put the numbers in

The density is 0.8.

The volume is 20.

The mass is what we want: we call it m.

0.8 = m20

Careful!

The mass goes on the top.

The unit, g/cm³, shows it: g on the top.

Careful: not 200.8 ✗

3 Remove the fraction

The bottom number is 20.

Times 20 will remove it.

We multiply both sides by 20, so they stay equal.

20 × 0.8 = ~~20 ×~~ m20

20 divided by 20 is 1.

So just m is left.

Write what is left.

20 × 0.8 = m

20 times 0.8 is 16.

16 = m

Whole numbers first: 20 times 8 is 160.

Then 1 decimal place.

20 × 8 = 160, 1 decimal place: 16

Let's swap the two sides, so m is on the left.

So m = 16.

m = 16

4 Check

Let's check: 16 divided by 20 is 0.8.

That is the density.

So the answer is right!

Check: 1620 = 0.8

So the mass is 16 g.

Let's look back.

First: write the rule.

Then: put the numbers in.

Then: remove the fraction.

Last: check.

Answer