Question

1 The area of the circle is 641 cm². What is the radius of the circle in cm? A=64 R=? Note: The figure is not drawn to scale A) 8 B 9 6 D) 5

Answer 1

Step 1: Let's recall the formula of the area of a circle, as follows:

`\text{Area = }\pi\ast r^2,\text{ where r is the radius of the circle}`

Step 2: Let's replace the values we know in the formula above:

`64\text{ }=\text{ 3.14 }\ast r^2\text{ }\Rightarrow\text{ r = }\sqrt{\frac{64}{3.14\text{ }}}=4.515\text{ centimetres}`

In case the area of the circle is 641, instead of 64:

`641\text{ = 3.14 }\ast r^2\text{ }\Rightarrow\text{ }\sqrt{\frac{641\text{ }}{3.14\text{ }}\text{ = 14.288 centimetres}}`

None of the choices given is correct, unless 4.515 is rounded to 5.