Chris purchased 10 maple trees, 6 oak trees, and some pine trees from the nursery. There is a 3 to 5 ratio of maple trees to pine trees. Which of the following numbers in the problem are needed to find the total number of pine trees that Chris purchased?

In order to find the actual number of pine trees, you need the initial ratio, plus one actual number. The initial ratio of maple trees to pine trees is 3 to 5, and the actual number of maple trees is 10. You do not need the fact that there were oak trees purchased. This piece of information does nothing to help you solve the ratio involving maple trees and pine trees.