The arithmetic mean of a set P of ten numbers is p, and the arithmetic mean of a set Q of twenty numbers is q. Find the arithmetic mean of all 30 numbers.

If set P has 10 numbers with an arithmetic mean of p, the sum of those 10 numbers is 10p.

If set Q has 20 numbers with an arithmetic mean of q, the sum of those 20 numbers is 20q.

To find the arithmetic mean of all thirty numbers: (10p + 20q) / 30/