Answer:
Matt ;
Used diameter of the ball instead of Radius
Explanation:
The volume of a sphere is given as :
4/3πr³
Radius, r = diameter / 2
Given that, the diameter = 15 cm ; The Radius = 15 / 2 = 7.5 cm
Matt made an error in his calculation by failing to covert the value of the diameter given to Radius.
By dividing the diameter by 2 = 15 / 2 = 7.5, we obtain the Radius, which is what Billy did in her own calculation.