The ASVAB Tutor Presents Answer to Circle Question

Mathematics Knowledge

As an ASVAB tutor, I place a strong emphasis on the importance of knowing formulas for the Mathematics Knowledge section.  No formulas will be provided on the test.  Make sure you know all the formulas for area, circumference, surface area and volume.

Yesterday I presented a Mathematics Knowledge question.

The question if on geometry and asks about a circle.

The question is:

If the area of a circle is 9p, what is the circumference?

A. 42

B. 84

C. 26

D. 52

You need to know the value of p.

p is 3.14.

You need to know the formula for the area of a circle.

The area of a circle is A = pr².

A = 9p

9p =pr²

9 = r²

r = 3

You need to know the formula for circumference of a circle.

The circumference of a circle is C =pd

d is diameter which is twice the radius

radius = 3 so diameter = 6

C =pd

C = 6p

C = 6 x 3.14 = 18.84

The correct answer is Choice B. 18.84.