10.5.1 Calculator Exploration: Introducing Pi

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

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

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

Find the pi key. It looks like this: The button shown is the Pi key.. When you want to use pi in a calculation, just click on the The button shown is the Pi key. key.

Activity Symbol Activity: Machine Components

Using the pi 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.

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The formula for the circumference of a circle is circumference equals pi multiplication diameter equation left hand side equals right hand side two multiplication pi postfix multiplication radius. When you want to multiply by pi, click on the The button shown is the Pi key. key.

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(a) The circumference of the circle is pi multiplication four almost equals 12.57 ft (rounded to 2 decimal places).

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(b) The radius of the circle is 3.2 in., so the circumference is two multiplication pi multiplication 3.2 almost equals 20.11 in (rounded to 2 decimal places).

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

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(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 = pi multiplication 1.6 yds. Then total distance round the edge of the component = open sum with, 3 , summands two plus two plus pi multiplication 1.6 close yds almost equals 9.03 yds (rounded to 2 decimal places).

To recap:

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

    circumference equation left hand side equals right hand side pi postfix multiplication diameter
    circumference equation left hand side equals right hand side two multiplication pi postfix multiplication radius

10.5.2 Protecting an Old Tree