17%
There are 30 students total. Out of those, there are 5 seniors. As a fraction: the probability is 5/30 or 1/6.
To convert to a percentage, you divide 5 by 30:
5/30=0.1666666667 which rounds to 0.17
To convert to a percentage, you must multiply the decimal by 100:
0.17*100=17
There is a 17% chance that the selected student will be a senior.