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Area of a circle
Description
Exercise Name: Area of a circle
Math Missions: 7th grade (U.S.) Math Mission8th grade (U.S.) Math Mission, High school geometry Math Mission, Algebra basics Math Mission, Mathematics I Math Mission
Types of Problems: 1

The exercise Area of a circle, appears under the 7th grade (U.S.) Math Mission8th grade (U.S.) Math Mission, High school geometry Math Mission, Algebra basics Math Mission and Mathematics I Math Mission. This exercise practices the relationship between radius, diameter, circumference and area.

## Types of Problems

There is one type of problem in this exercise:

1. Find the requested measure from the given one: This problem gives either the radius, diameter or circumference of a circle. The student is asked to find one of the other measures.

## Strategies

Knowledge of the four basic circle constants is an advantage on this exercise.

1. The circle constants are radius, diameter (which is twice the radius), circumference (which is ${2\times\pi\times r}$ or also ${\pi\times d}$) and the area formula (which is ${\pi\times r^2}$, though not needed on this exercise.)
2. The circumference formula can be remembered with the mnemonic "Cherry pies are delicious."
3. The area formula can be remembered with the mnemonic "Apple pies are too."
4. All four circle constants can be listed with the acronym CARD.

## Real-life Applications

1. Area and perimeter are used in many jobs such as architecture and interior design.
2. The ancient Egyptians from over 4000 years ago were very good at shapes and geometry. Every time the Nile burst its banks and flooded the planes, they had to use geometry to measure their gardens and fields all over again.