Maths Question

Question

What is the diameter, to the nearest tenth of a meter, of a circle whose area is 15.9 square meters?

 

1.    5 meters

 

2.    2.3 meters

 

3.    4.5 meters

 

4.     9 meters

Answer 1

the underlying formula that we want to use to solve this one is the area of a circle formula

A = pi * r^2, meaning that

r = sqrt(A/pi)

for this set of values that means that

r = sqrt(15.9 / pi) = 2.25

then you can find the diameter by multiplying by 2!

d = 2r = 2(2.25) = 4.5

meaning that the diameter of this circle is approximately 4.5 meters

Answer 2

A = πr²                 formula for area

15.9 = πr²            substitute values

5.06 = r²              divide both sides by π

2.249 ≈ r              take square root of both sides.

4.4993 ≈ d           multiply both sides by 2.

 

The diameter is 4.5 meters.