Question

There are three choices of jellybeans - grape ,cherry and orange. if the probability of getting a grape is 3/10 and the probability of getting cherry is 1/5, what is the probability of getting orange

Answer 1

When looking at probabilities, two ideas are always true.

1) Any probability is more than 0.

2) The sum of all the probabilites is 1.

Idea #2 works here. (For example, think of how a die has six things and the probability of each is 1/6. So 1/6 + 1/6 + 1/6 + 1/6 + 1/6 + 1/6 = 1.) Let G = the probability of grape, C = probability of cherry and O = the probability of orange. From Idea #2, G + C + O = 1. Since we know G and C, then

3/10 + 1/5 + O = 1.

3/10 + 2/10 + O = 1

5/10 + O = 1

O = 5/10

Thus, the probability of an orange jelly bean is 5/10 = 1/2.