GCSE(F), GCSE(H),

A more accurate answer, when calculating circle-based objects, can be obtained by not using a value of *π*, but to leave it as a **constant**.

Questions may ask for the answer to be given *in terms of π*. In this instance, do not use a value for *π*, show the answer instead as a multiple of *π*.

1. A circle has a radius of 8 cm. What is the area of the circle? Give your answer in terms of *π*.

Answer: 64*π* cm^{2}

Area of a circle ` = pir^2`

`A = pi xx 8^2`

`A = 64pi` cm^{2} (answer in terms of *π*)

2. A deep underwater sphere to explore the bottom of the ocean has a diameter of 3m. What is the volume of the sphere? Give your answer in terms of *π*.

Answer: 4.5*π* m^{3}

Volume of sphere `= frac(4)(3)pir^3`

`V = frac(4)(3) xx pi xx (frac(3)(2))^3` (change diameter to radius)

`V = 4.5pi` m^{3}

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