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Maths Exercices

Make predictions

One of the most powerful abilities of probability is the ability to make predictions.  By knowing the probability of an event occurring, we can make a guess as to how many times the event will occur over time.

Out of the people who have already signed up for a genetics lecture, 6 people have blue eyes while 4 people do not. Considering this data, how many of the next 30 people to sign up should you expect to be blue-eyed?

First write the experimental probability as a fraction in simplest form.

The experimental probability is

We can predict the outcome of the second set of trials by assuming that the ratio will be the same as in the first set of trials. Write a proportion by setting the two ratios equal to each other, then solve.


3×30  =  5n Find the cross products

90  =  5n Simplify

18  =  n Divide both sides by 5

You should expect 18 of the next 30 people to be blue-eyed.