Probability of the spinner

Question

Marcia will use the spinner below. 

 

Letters are: Z,Q,M,R,Q,S,M,Q

 

Marcia is hoping the pointer will stop on a letter that she has chosen. The probability that the pointer will stop on Marcia's letter is 3/8. What is the letter that Marcia has chosen?

Answer 1

The probability of any letter being chosen is:

(ways that letter can be chosen) / (total ways a letter can be chosen)

 

For example, there is only one way that Z can be chosen, since there is only one Z for the pointer to stop on. The total ways a letter can be chosen is eight, since there are eight total letter on the spinner.

 

That makes the chance of Z being chosen 1/8.

You might also see this written as P(Z)=1/8. This just means the probability of the event Z is one in eight.

We can do the same thing for all the letters.

P(Z)+1/8

P(Q)=3/8

P(M)=2/8=1/4

P(R)=1/8

P(S)=1/8

 

Since the probability that the pointer will stop on Marcia's letter is 3/8, she must be thinking of Q.