- Math 7 Quiz 18 Notes -

Area of a triangle

A = 1/2 bh

Area of a trapezoid

A = 1/2 h (b1 + b2)

Area of a parallelogram

A = bh

Area of a circle

A = pi r²

Find the area of this parallelogram... b= 8 m h = 4 m NOTE: this parallelogram will be on a grid, so you will have to COUNT THE SQUARES on the grid to find the base and height.

How to solve... 1) write out the formula for area of a parallelogram --> A = bh 2) Plug in the numbers given for each part of formula, and multiply to solve --> A = (8 m)(4 m) A = 32 m² *Your answer MUST BE squared!

Find the area of this trapezoid... h = 4in b1 = 3in b2 = 12in

How to solve... 1) write out the formula for area of a trapezoid --> A = 1/2 h (b1 + b2) 2) Plug in the numbers given for each part of formula 3) Add the bases together --> (3 in + 12 in) = 15 in. 4) Multiply all the numbers together--> A = 1/2(4 in)(15 in) A = 30 in² *Your answer MUST BE squared!

Find the area of this circle... r = 4km

How to solve... 1) write out the formula for area of a circle --> A = pi r² pi = 3.14 2) Plug in the numbers given for each part of formula, and solve --> A = (3.14)(4km)² NOTE: First, "square" the radius. So 4² is 16. Then, mutiply... A = (3.14)(16) A = 50.24 km² *Your answer MUST BE squared!

Find the area of this circle... d = 10 yd

How to solve... 1) write out the formula for area of a circle --> A = pi r² pi = 3.14 2) They gave you diameter, so change to radius. Remember, radius is half of the diameter. Divide the diameter given by 2; the answer is your radius (r). r = d/2 r = 10yd/2 r = 5 yd 3) Plug in the numbers given for each part of formula, and solve --> A = (3.14)(5yd)² NOTE: First, "square" the radius. So 5² is 25. Then, mutiply... (3.14)(25) A = 78.5 yd² *Your answer MUST BE squared!

Find the area of this triangle... b = 3 m h = 3 m NOTE: this triangle will be on a grid, so you will have to COUNT THE SQUARES on the grid to find the base and height. And, each grid square will be equal to 4 m -> So, if the base is 3 squares long, then multiply for the CORRECT BASE... 3 squares = 3x4m = 12 m

How to solve... 1) write out the formula for area of a triangle --> A = 1/2 bh 2) Multiply both the base (b = 3) and the height (h = 3) by 4, to get the correct answer. 3 m x 4 m = 12 m 3 m x 4 m = 12 m 3) Plug in the numbers given for each part of formula, and multiply to solve --> A = 1/2 (12 m)(12 m) A = 72 m² *Your answer MUST BE squared!

Find the area of this triangle... b= 6 ft h = 5 ft NOTE: this triangle will be on a grid, so you will have to COUNT THE SQUARES on the grid to find the base and height.

How to solve... 1) write out the formula for area of a triangle --> A = 1/2 bh 2) Plug in the numbers given for each part of formula, and multiply to solve --> A = 1/2 (6 ft)(5 ft) A = 15 ft² *Your answer MUST BE squared!