Step by step
The question
Question: find the area of this L-shape: 10 by 8, with a 4 by 3 corner cut out.
1 Split into rectangles
This shape is not a rectangle.
One line cuts it into two rectangles.
We call them top and bottom.
2 Find the missing sides
The top side is the whole 10, take away the 4 cut out.
10 minus 4 is 6.
10 − 4 = 6
The right side is the whole 8, take away the 3 cut out.
8 minus 3 is 5.
8 − 3 = 5
3 Area of each part
The top rectangle is 6 by 3.
6 times 3 is 18.
top = 6 × 3 = 18
The bottom rectangle is 10 by 5.
10 times 5 is 50.
bottom = 10 × 5 = 50
4 Add the parts
The whole area is the two parts added.
A = 18 + 50
18 plus 50 is 68.
So the area is 68 square units.
A = 68
5 Check
Let's check another way: the whole 10 by 8 rectangle, take away the corner.
10 × 8 − 4 × 3 = 80 − 12 = 68
We get 68 again.
So the area is right!
Let's look back.
First: split into rectangles.
Then: find the missing sides.
Then: area of each part.
Then: add the parts.
Last: check.
Answer
A = 68