Write the Area of a circle formula and solve for r.
Write the Circumference formula and solve for r.
Which of these formulas are proportional and why?
5 Problems - SHOW ALL WORK!
The circular fountain in front of the courthouse has a circumference of 29.5 feet. What is the radius of the fountain? Round to the nearest tenth.
Joni has a circular garden with a diameter of 14 1 2 feet. If she uses 2 teaspoons of fertilizer for every 25 square feet of garden, how much fertilizer will Joni need for her entire garden? Round to the nearest tenth. x=3
A lawn sprinkler sprays water 78.5 square feet area and sprays in every direction as it rotates. What is the length of the sprinkler’s stream of water?
The distance around the wheel of a truck is 9.42 feet. What is the diameter of the wheel?
Ms. Van Rybroek’s favorite part of the pizza is the crust. Which size pizza should she order to get 37.68 inches of crust?
Area of a circle formula: A = πr^2
Solve for r:
r = √(A/π)
Circumference formula: C = 2πr
Solve for r:
r = C / (2π)
These formulas are proportional because the relationship between the radius (r) and the area (A) or circumference (C) remains constant.
1. Given Circumference = 29.5 feet
r = 29.5 / (2π) ≈ 4.7 feet
2. Given Diameter = 14 1/2 feet, Radius = 7 1/4 feet
Area = π(7.25)^2 ≈ 165.1 square feet
Amount of fertilizer needed = 165.1 / 25 * 2 ≈ 13.2 teaspoons
3. Given Area = 78.5 square feet
Radius = √(78.5/π) ≈ 5 feet
Length of water stream = 2 * 5 ≈ 10 feet
4. Given Circumference = 9.42 feet
r = 9.42 / (2π) ≈ 1.5 feet
Diameter = 2 * 1.5 = 3 feet
5. Given Crust length = 37.68 inches
r = 37.68 / (2π) ≈ 6 inches
Ms. Van Rybroek should order a pizza with a 12-inch diameter to get 37.68 inches of crust.