Density 2.5 g/cm³, volume 12 cm³, find the mass Step by Step

Step by step

The question

Question: find the mass when the density is 2.5 g/cm³ and the volume is 12 cm³.

Density 2.5 g/cm³, volume 12 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 2.5.

The volume is 12.

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

2.5 = m12

Careful!

The mass goes on the top.

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

Careful: not 122.5 ✗

3 Remove the fraction

The bottom number is 12.

Times 12 will remove it.

We multiply both sides by 12, so they stay equal.

12 × 2.5 = ~~12 ×~~ m12

12 divided by 12 is 1.

So just m is left.

Write what is left.

12 × 2.5 = m

12 times 2.5 is 30.

30 = m

Whole numbers first: 12 times 25 is 300.

Then 1 decimal place.

12 × 25 = 300, 1 decimal place: 30

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

So m = 30.

m = 30

4 Check

Let's check: 30 divided by 12 is 2.5.

That is the density.

So the answer is right!

Check: 3012 = 2.5

So the mass is 30 g.

Let's look back.

First: write the rule.

Then: put the numbers in.

Then: remove the fraction.

Last: check.

Answer