Step by step
The question
Question: find the width w of a rectangle with area 35 cm² and length 7 cm.
1 Write the rule
The area of a rectangle is length times width.
So A = length × width.
2 Put the numbers in
The area is 35 and the length is 7.
So 7 × w = 35.
Careful!
The area is times, not plus.
So we divide by 7.
We do not take it away.
3 Remove the × 7
We want w by itself.
The times 7 is in the way.
To remove times 7, we divide by 7.
We do it on both sides.
Why both sides?
The = sign means both sides are the same amount.
If we change only one side, they are not the same any more.
7 divided by 7 is 1.
So just w is left.
35 divided by 7 is 5 cm.
So the width is 5 cm.
4 Check
Let's check: length times width, 7 times 5.
We get 35, the area.
So the width is right!
Let's look back.
First: write the rule.
Then: put the numbers in.
Then: remove the × 7.
Last: check.