## FANDOM

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

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

## 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 user is asked to find one of the other measures.

## Strategies

Knowledge of the four basic circle constants is an advantage on this exercise (although only three of them are used).

1. The circle constants are radius, diameter (which is twice the radius), circumference (which is ${2\pi\times r}$ 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

There are many uses for radius, diameter, and circumference in real life:

1. Car makers use it measure car wheels to make sure they fit.
2. Race engineers use it to find out what size tire gives them the most performance.
3. Bakers use it to make pies and other circular-shaped foods.
4. Military engineers use it for balancing helicopter blades.
5. Aircraft engineer use it for propeller efficiency.