Question

A spinner contains the numbers 1 through 40. What is the probability that the spinner will land on a number that is not a multiple of 9? Give your answer as a fraction.

Answer 1

To solve this question, let us first list out the multiples of 9 between 1 and 40

The multiples of 9 are 9, 18, 27, 36.

To get the probability that the spinner lands on a number that is not a multiple of 9.

We can use the relationship:

$1-P(9)$

Where P(9) is the probability of obtaining a multiple of 9

Let us get P(9) first. Since there are 4 multiples of 9 between 1 and 40

$P(9)=\frac{n\nu\text{mber of multiples }}{total\text{ numbers}}=\frac{4}{40}=\frac{1}{10}$

Next, we will subtract this value from 1

$1-\frac{1}{10}=\frac{10-1}{10}=\frac{9}{10}$

The answer is:

$\frac{9}{10}$