Just as the symbol n P r represents the number of permutations of n objects taken r at a time, n C r represents the number of combinations of n objects taken r at a time. In the above example, if we k...Just as the symbol n P r represents the number of permutations of n objects taken r at a time, n C r represents the number of combinations of n objects taken r at a time. In the above example, if we knew that there were three combinations, we could have found the number of permutations by multiplying this number by 2!. That is because each combination consists of two letters, and that makes 2!
