instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: what is the greatest prime factor of 2 ^ 10 - 1 ?
answer:
3


question:
Problem: if the sides of a cube are in the ratio 5 : 3 . what is the ratio of their diagonals ?
answer:
5 : 3'


question:
Problem: two spherical balls lie on the ground touching . if one of the balls has a radius of 9 cm , and the point of contact is 10 cm above the ground , what is the radius of the other ball ( in centimeters ) ?
answer:

90 / 8