# 10.5.1 Calculator Exploration: Introducing Pi

The calculator can be accessed on the left-hand side bar under Toolkit.

In this exploration, you will use the calculator for formulas involving

The calculator uses a 14-decimal place approximation for , precise enough for most calculations.

Find the key. It looks like this: . When you want to use in a calculation, just click on the key.

## Activity: Machine Components

Using the key on the calculator, work out the perimeters for each of the following machine components. Assume that the measurements are sufficiently accurate to allow answers to 2 decimal places.

### Comment

The formula for the circumference of a circle is . When you want to multiply by , click on the key.

### Answer

(a) The circumference of the circle is (rounded to 2 decimal places).

### Answer

(b) The radius of the circle is 3.2 in., so the circumference is (rounded to 2 decimal places).

### Comment

Break this more complicated shape up into simpler shapes that you know how to calculate the circumference.

### Answer

(c) The perimeter is made up of two semicircular ends of diameter 1.6 yards and two straight edges of length 2 yards.

The two semicircular ends together form a circle, so the distance around the ends of the component will be the same as the distance around a circle of diameter 1.6 yards.

This distance = . Then total distance round the edge of the component = (rounded to 2 decimal places).

## To recap:

- When you want to use in a calculation, use the key on the calculator.
- The circumference of a circle is its perimeter.
To calculate the circumference you can use one of two formulas:

10.5 Perimeters