What is the smallest number of science students who could be studying biology?

Question

If 20% of the science students at central high study only physics, 25% study only chemistry and the rest study only biology, what is the smallest number of science students who could be studying biology?

Please explain step by step.

Answer 1

In percentages, it is easy to assume 100 as the total. This allows us to equate the percentage with an actual number or students.

So 20% students studying only physics equates to 20 students studying only physics and 25% students studying only chemistry equates to 25 students studying chemistry. Adding this together we have:

25 + 20 = 45

To attain the number of science students studying biology, we subtract this number from 100.

100 - 45 = 55.

The smallest number of science students studying biology is 55.