Question

Mariah has a spinner that has 10 equal sections, each containing a different number from 1 to 10. Mariah determines about how many times the spinner will land on a number that is greater than 7 in 250 spins, and her work is shown below.

P (number greater than 7) = StartFraction Number greater than 7 over Total number of sections EndFraction times number of spins = StartFraction 4 over 10 EndFraction (250) = 100.

What mistake did Mariah make, if any?
Mariah has the formula reversed; it should be the total number of sections over the numbers greater than 7.
Mariah should have used a 3 in the numerator because there are 3 numbers greater than 7.
Mariah should multiply by the number of sections in the spinner rather than the total number of spins.
Mariah calculated the prediction correctly and did not make any mistakes.
A B C or D

Answer 1

B

There are only 3 numbers greater than 7 (8, 9, 10), so the probability is 3/10 and the expected count is (3/10)(250) = 75, not 100.