Explanation:
assuming 90° is the central angle measure then the degree measure of the arc would be 90°
though the question asks for length
to do this create a ratio of the degree measurement of the arc divided by the total degree measure of a circle which would be
90/360
next think about circumference, it's the measure of the length around a circle. that would be relevant to what the question is asking so calculate it the formula is C=2*pi*r
calculate and the circumference is 24pi
next multiply the total circumference by the ratio for the section we want in this case 90/360
arc length = 24pi * 90/360 = 6pi
therefore the answer is 6pi or 18.84 substituting 3.14 for pi