Transcript Area and perimeter of irregular shapes

Area and perimeter of irregular
shapes
Pick up 2 different colored highlighters
for your notes today
What is the perimeter of this irregular shape?
To find the perimeter, you first need to make sure you have all of the information you need.
We are missing 2
numbers, you subtract or
add to find these
numbers.
19yd
18yd 7yd
30yd
23 yd
37yd
Highlight the vertical sides all of the same color to help you.
Subtract 30 and 23 The missing side is 7
Highlight the horizontal sides all of the same color to help you.
Subtract 37 and 19 The missing side is 18
Add all of the sides up
The perimeter is 134 yd
What is the area of this irregular shape?
To find the area of an irregular shape you need to split it up into shapes you already know.
I see 2 rectangles,
so I’m going to split
my shape into 2
rectangles.
19yd
18yd 7yd
133
30yd
23yd
Find the area of each rectangle now
851
37yd
To find the area of the top rectangle you multiply 7 and 19 and get….
To find the area of the bottom rectangle you multiply 23 and 37 and get….
To get the
total area
you just need
to add those
amounts
together
984 sq. yd
What is the perimeter of this irregular shape?
20in
3in
13in
7in
13in
19in
9in
Highlight the sides of your shape.
20in
Find the missing numbers for your shape
Now that you have all of sides figured out you just need to add to find the perimeter
The perimeter is…..
104 in
What is the area of this irregular shape?
20 in
3 in
39
13 in
7 in
13in
133
19 in
7
117
20 in
9 in
Remember, you need to split it up into shapes you know formulas for.
I see 3 rectangles in this shape
Draw in your imaginary lines to see the rectangles
The area is…..
Find the area of each rectangle
289 sq. in
Multiply 13 and 3 to get…..
Multiply 13 and 9 to get …..
Multiply 19 and 7 to get …..
Add all of the areas together
How do you find the area of the shaded region?
20 ft
10 ft
12 ft
22 ft.
Find the area of the big rectangle by multiplying 22 and 20 together
440
Find the area of the small rectangle by multiplying 12 and 10 together
120
Subtract the 2 totals to get the area of the shaded region
320 sq. ft