Thread: Probabilty word problem

HI everyone,

I have a hard time understanding this concept of probability. Can you help me to solve these problems?

1)An ice cream store offers 19 different flavors of ice cream. How many triple-scoop ice cream cones are possible if each scoop must be a different flavor and the flavors can be in any order?

2)A hospital nursery with 22 babies contains exactly 11 girls and 11 boys. If the chances of a woman giving birth to a boy or a girl are the same, what is the probability that exactly 11 out of the 22 babies are girls?

3)A group of 5 children are each to choose one popsicle from a box of 12: 4 grape, 4 cherry, and 4 orange. What is the probability that each child will get the flavor they want?

4)A tire company tested a particular model of super radial tire and found the tires to be normally distributed with respect to wear. The "average" (mean) tire wore out at 41,000 miles, and the standard deviation was 4000 miles. Approximately what percent of the tires are likely to wear out before 40,200 miles?


Thank you

First, I assume you know the "fundamental theorem of counting"- if you can choose A in m ways and choose B in n ways- and your choice for A does not affect your choice for B- then you can choose A and B in mn different ways, the product of the two numbers.

1) There are 19 different types of icecream for the first scoop. Since you cannot use that again for the second, there are 18 different types for the second scoop. Since you cannot use either of the first two kinds of ice cream again, you have 17 choices for the third scoop.