How much paint do we need to paint

Square Area = s 2 (s = side length) Rectangle Area = lw (l

You can justify the area formula for triangles as follows: The area of a

Be careful when identifying the height of a triangle! The height is NEVER a

Ex 1: Find the area of. . a. A square whose sides have length

b. A rectangle whose length is 5 m and width is 11 m. 5

c. A triangle whose side lengths are 3 in, 4 in, and 5 in.

Ex 2: Find the indicated side length. a. A square with area 256 in

b. A rectangle with area 345 ft and length 15 ft 23 ft 15

c. A triangle with area 12 mm and a base length of 6 mm.

Parallelogram Area = bh (b = base and h = height) Trapezoid Area =

You can justify the area formula for parallelograms as follows: h The area of

Ex 3: Find the area of parallelogram ABCD B C 9 16 A E

Ex 3: Find the area of parallelogram ABCD C B 9 16 A E

Ex 4: Find the area of trapezoid WXYZ. Y(2, 5) X(1, 1) Z(5, 5)

Ex 5: The area of a trapezoid is 135 cm 2, height is 9,

Ex 6: Find the area of the rhombus. 9 12

Ex 7: The area of a rhombus is 40 in 2 and one of

Circle Area = Ex 8: Find the area if the radius Leave your answer

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How much paint do we need to paint all the rooms in our house? kitchen bedroom TV room

Square Area = s 2 (s = side length) Rectangle Area = lw (l = length and w = width) Triangle Area = ½bh (b = base and h = height)

You can justify the area formula for triangles as follows: The area of a triangle is half the area of a parallelogram with the same base and height. Area of a Parallelogram = bh Area of a Triangle = ½bh

Be careful when identifying the height of a triangle! The height is NEVER a side of a triangle unless the triangle is RIGHT. h h h

Ex 1: Find the area of. . a. A square whose sides have length 8 cm A = s 2 A = 82 A = 64 cm 2

b. A rectangle whose length is 5 m and width is 11 m. 5 m 11 m 5 m A = lw A = (5)(11) A = 55 m 2

c. A triangle whose side lengths are 3 in, 4 in, and 5 in. 4 in 5 in 3 in A = ½ (4)(3) A = ½ (12) A = 6 in 2

Ex 2: Find the indicated side length. a. A square with area 256 in 2. 16 in A = s 2 256 = s 2 16 = s

b. A rectangle with area 345 ft and length 15 ft 23 ft 15 ft A = lw 345 = 15 w 23 ft = w

c. A triangle with area 12 mm and a base length of 6 mm. 4 mm 6 mm A = ½ bh 12 = ½ (6)h 12 = 3 h 4 mm = h

Parallelogram Area = bh (b = base and h = height) Trapezoid Area = ½ h (b 1 + b 2) Rhombus Area = ½d 1 d 2 (d = diagonal)

You can justify the area formula for parallelograms as follows: h The area of a parallelogram is the area of a rectangle with the same base and height. Area of Parallelogram = bh

Ex 3: Find the area of parallelogram ABCD B C 9 16 A E 12 D Method 1 Use AB as the base and BE as the height. 12 F

Ex 3: Find the area of parallelogram ABCD C B 9 16 A E 12 D 12 F Method 2 You get the same Use AD as the base and answer. CF as the height.

Ex 4: Find the area of trapezoid WXYZ. Y(2, 5) X(1, 1) Z(5, 5) W(8, 1) Count the blocks for height, base 1, and base 2.

Ex 5: The area of a trapezoid is 135 cm 2, height is 9, and one bases is 11. Find the other base.

Ex 6: Find the area of the rhombus. 9 12

Ex 7: The area of a rhombus is 40 in 2 and one of the diagonals is 8 in. Find the other diagonal.

Circle Area = Ex 8: Find the area if the radius Leave your answer in terms of pi unless stated otherwise. .