120 students are interviewed.

72 students drink Monster with the ratio of those drinking the regular type to the sugar free being 5:3.

The remaining students drink Red Bull, with the ratio of those drinking the regular type to the sugar free being 3:1.

What is the probability that a student chosen at random drinks sugar free Red Bull.

Give your answer as a decimal

In this question, we are concerned with calculating probability that out of the 120 students interviewed, a student chosen at random drinks sugar free red bull.

Mathematically, the probability is = number of students that drinks sugar free red bull/Total number of students interviewed

We know the total number of students interviewed, but we do not know the number of students that drink sugar free red bull.

Now looking at the question, we can see that all the students interviewed has the choice of having only to drinks, monster or red bull.

Since 72 students drink monster, the number of students that take red bull = 120 - 72 = 48

Now from this 48, we have a ratio. The ratio of regular type to sugar free is 3:1. The number taking sugar free is thus 1/4 × 48 = 12 students

The probability of choosing a student that drinks sugar free red bull is thus 12/120 = 1/10 = 0.1