Question

A spinner is numbered from 1 through 10 with each number equally likely to occur. What is the probability of obtaining a number less than 3 or greater than 8 in a single spin?

Answer 1

`P = 0.4`

Explanation:

If each number X has the same probability of occur then the probability for each number is:

`P = (1)/(10)`

Note that X is a discrete random variable, and the probability of obtaining an X number is independent for each trial.

So the probability that X is less than 3 is:

`P (X <3) = P (1) + P (2)`

But
`P (1) = P (2) = (1)/(10)`

So:

`P (X <3) = P (1) + P (2) = (2)/(10) = (1)/(5)`

Also

`P (X> 8) = P (9) + P (10) = (1)/(10) = (1)/(5)`

Finally

`P (X <3\ or\ X> 8) = (1)/(5) +(1)/(5) = (2)/(5) = 0.4`