Step by step
The question
Question: find the density when the mass is 240 g and the volume is 30 cm³.
Mass 240 g, volume 30 cm³. Find the density.
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 mass is 240.
The volume is 30.
d = 24030
3 Work it out
Careful!
The mass goes on the top.
The unit, g/cm³, shows it: g on the top.
Careful: not 30240 ✗
240 divided by 30 is 8.
density = 8 g/cm³
Both end in a zero: we cross it out first.
24 divided by 3 is 8.
240 ÷ 30 = 24 ÷ 3 = 8
So the density is 8 g/cm³.
4 Check
Let's check.
8 in each cm³, for 30 cm³: 8 times 30 is 240.
That is the mass.
So the answer is right!
8 g in each cm³: 8 × 30 = 240 g
Let's look back.
First: write the rule.
Then: put the numbers in.
Then: work it out.
Last: check.
Answer
240 ÷ 30 = 24 ÷ 3 = 8