instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: 30 pens and 75 pencils were purchased for 750 . if the average price of a pencil was 2.00 , find the average price of a pen .
answer:
20


question:
Problem: three 7 faced dice are thrown together . the probability that all the three show the same number on them is ?
answer:
1 / 49


question:
Problem: the sum of the first n positive perfect squares , where n is a positive integer , is given by the formula n ^ 3 / 3 + c * n ^ 2 + n / 6 , where c is a constant . what is the sum of the first 20 positive perfect squares ?
answer:

2,87