The answer is 95%
This is something you should memorize. Specifically it is from the Empirical Rule (or 68-95-99.7 rule) which gives rough approximations of areas under the curve.
Answer:
he needs to get a 91 to have a mean score of 90
Step-by-step explanation:
add up all the known scores to get 629
let 's' = lowest test score
(629 + s) ÷ 8 = 90 [we divide by 8 because there are 7 known and 1 unknown score)
cross-multiply to get:
629 + s = 720
s = 720-629
s = 91
The numbers are 3 and -30 They multiply and give -90 And add to give-27
