Step by step
The question
Question: find the area of the rectangle with corners (−3, 1), (2, 1), (2, 5), (−3, 5).
rectangle: (−3, 1), (2, 1), (2, 5), (−3, 5)
1 Plot the points
We put the corners on the grid.
Corner A is (−3, 1).
And so on.
We join them in order.
2 Find the side lengths
A B: the same y, so it goes across.
Its length is the bigger x minus the smaller: 2 minus −3 is 5.
= AB: 2 − (−3) = 5
Careful!
−3 is on the other side of 0.
Minus a negative is plus: 2 plus 3.
Careful: not 2 − 3 = -1 ✗
B C: the same x, so it goes up and down.
Its length is the bigger y minus the smaller: 5 minus 1 is 4.
= BC: 5 − 1 = 4
3 Area
The area of a rectangle is length times width.
= area = length × width
5 times 4 is 20 square units.
= area = 5 × 4 = 20 square units
4 Check
Let's check: count the squares inside.
4 rows of 5 squares: 20.
So the answer is right!
4 rows of 5 squares = 20 squares
Let's look back.
First: plot the points.
Then: find the side lengths.
Then: area.
Last: check.
Answer
= area = 5 × 4 = 20 square units