# 6th Grade - Using Pi

 Grade Level: 6th Skill: Geometry Topic: Using Pi Goal: Know common estimates of pi (3.14; 22/7) and use these values to estimate and calculate the circumference and the area of circles; compare with actual measurements. Skill Description: The value of pi can be represented as a decimal (3.14) or a fraction (22/7). Use the decimal estimate when solving problems with decimals and whole numbers (i.e. radius = 4.5). Use the fraction estimate of pi when working with problems involving fractions (i.e. radius = 5 1/4 ). A formula can be used to calculate the circumference or area of a circle. The formula for circumference is C = πd or C = 2 π r. The formula to be used to calculate the area of a circle is A = πr 2. Estimations of the circumference or area of a circle can be made using the formulas and knowing that pi is about 3. Calculate the actual circumference and/or area of a circle can be done using the correct formula and the common estimate for pi. Compare actual measurements with estimates to verify reasonableness of results.

## Building Blocks/Prerequisites

### Sample Problems

 (1) A circle has a diameter of 6 ¾ inches. What is the circumference of the circle? (42.39 in.) (2) A circle has a radius of 6.75 inches. What is the area of the circle to the nearest whole number? (143 cm 2 ) (3) A can lid has a diameter of 9 cm. Use the correct formula to find the circumference of the can lid. (28.26 cm) (4) A Frisbee has a radius of 4 in. Solve to find circumference. (25.12 cm) (5) A car tire has diameter of 12 inches. Solve to find area. (113.04 in. 2 )

### Online Resources

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