Step by step
The question
Question: find the height h of a triangle with area 15 square units and base 4.
1 Write the rule
A triangle is half of the box around it.
So its area is half of base times height: A = ½ × b × h.
Now put the numbers in: A = 15 and b = 4.
Careful!
Do not forget the half.
The triangle is only half of the box.
2 Half of the base
Half of 4 is 2.
So 2 × h = 15.
3 Remove the × 2
We want h by itself.
The times 2 is in the way.
To remove times 2, we divide by 2.
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.
2 divided by 2 is 1.
So just h is left.
15 divided by 2 is 7.5.
So the height is 7.5.
4 Check
Let's check: half of base times height.
We get 15, the area.
So the height is right!
Let's look back.
First: write the rule.
Then: half of the base.
Then: remove the × 2.
Last: check.