Complete question :
The average amount that a college student spends on a textbook is $205 with a
standard deviation of $35. What is the probability that a student spends:
A. between $10 and $310?
Answer:
0.999
Step-by-step explanation:
Mean, m = 205 ; Standard deviation, s = 35
Z = (x - m) / s
x = 310
Z = (310 - 205) / 35 = 3
P(z < 3) = 0.99865
x = 10
Z = (10 - 205) / 35 = - 5.57
P(Z < - 5.5)
P(z < 3) - P(z < - 5.5)
0.99865 - 0
= 0.999
