Step by step
The question
Question: find the perimeter of the rectangle with corners (−2, −1), (3, −1), (3, 2), (−2, 2).
rectangle: (−2, −1), (3, −1), (3, 2), (−2, 2)
1 Plot the points
We put the corners on the grid.
Corner A is (−2, −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: 3 minus −2 is 5.
= AB: 3 − (−2) = 5
Careful!
−2 is on the other side of 0.
Minus a negative is plus: 3 plus 2.
Careful: not 3 − 2 = 1 ✗
B C: the same x, so it goes up and down.
Its length is the bigger y minus the smaller: 2 minus −1 is 3.
= BC: 2 − (−1) = 3
3 Perimeter
The perimeter is the way round: all four sides.
= perimeter = all four sides
5 plus 3 plus 5 plus 3 is 16 units.
= perimeter = 5 + 3 + 5 + 3 = 16 units
4 Check
Let's check: opposite sides are the same.
So it is 2 times 5 plus 3: 2 times 8 is 16.
So the answer is right!
2 × (5 + 3) = 2 × 8 = 16
Let's look back.
First: plot the points.
Then: find the side lengths.
Then: perimeter.
Last: check.
Answer
= perimeter = 5 + 3 + 5 + 3 = 16 units