Exam grades: Scores on a statistics final in a large class were normally distributed with a mean of 75 and a standard deviation of 9. Use the TI-84 PLUS calculator to answer the following. Round the answers to at least two decimals. (a) Find the 41st percentile of the scores. (b) Find the 74th percentile of the scores. (c) The instructor wants to give an A to the students whose scores were in the top 8% of the class. What is the minimum score needed to get an A

Solution :

Using the TI-84 PLUS calculator

a). Area : 0.41

μ = 75

σ = 9

InvNorm(0.41,75,9)

= 72.95209525

Therefore, the 41st percentile of the scores is 72.95209525

b).  Area : 0.74

μ = 75

σ = 9

InvNorm(0.74,75,9)

= 80.79010862

Therefore, the 74st percentile of the scores is 80.79010862

c). 8%

So,  Area : 0.92

μ = 75

σ = 9

InvNorm(0.92,75,9)

= 87.64564405

Therefore, X =  80.79010862

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so:

hi! i think the answer is 1/2 : )