6) The amount of Jen's monthly phone bill is normally distributed with a mean of $70 and a standard

deviation of $10. What percentage of her phone bills are between $40 and $100?

A) 68.26%

B) 99.99%

C) 95.44%

D) 99 74%

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7) At one college, GPA's are normally distributed with a mean of 26 and a standard deviation of 0.5.

What percentage of students at the college have a GPA between 2.1 and 3.17

A) 84.13%

B) 68.26%

C) 95.44%

D) 99.74%

i) The correct option is D.) 99.74%

ii) The correct option is B.) 68.26%

Step-by-step explanation:

i) P (10≤X≤70) = P ((10-40) / 10 ≤Z≤ (70-40) / 10) = Pr (-3≤Z≤3)

= 0.9987 - 0.0013 = 0.99734

Therefore the percentage of Jen's monthly phone bills are between $40 and $100 is D.) 99.74%

ii) P (2.1≤X≤3.1) = P ((2.1 - 2.6) / 0.5 ≤ Z ≤ (3.1-2.6) / 0.5) = Pr (-1 ≤Z ≤1))

= 0.8413 - 0.1587 = 0.6826

Therefore the percentage of students at college have a GPA between 2.1 a, d 3.1 is B.) 68.26%