posted by HM on .
a spinner has regions numbered through 1-21
what is the probability that the spinner will stop on an even number or a multiple of 3..
I am confused.
I keep coming up with 17/21
but the real answer is 2/3
how how how ?
Even number = 10/21
Multiple of 3 = 7/21
10/21 + 7/21 = 17/21
Guess what? I keep coming up with 17/21 too.
You need to remember that 6 is also an even number, so you can't count it twice as it is only one number. So you have 10 possible even numbers, plus 7 possible numbers that are multiples of 3, minus 1 multiple of 3 (the number 6) because you already counted it in your even numbers.
A spinner has 5 sections labeled 1 through 5. The probability of randomly spinning an even number is 2/5. What is the probability of not spinning an even number?