Permutations or combinations? Combinations Answer: 715
Practice makes perfect
We want to find how many ways there are to select 4 out of 13 different colored balloons. Note that, in this case, the order is not important. Thus, the situation involves combinations. To calculate the answer, we will use the formula for combinations of n objects taken r at a time.
_n C_r = _n P_r/r! ⇔ _n C_r = n!/(n-r)!r!
In our exercise, n= 13 and r= 4. Let's substitute these values into the above formula.
