Learning theory students in a psychology experiment were given an exam and then retested monthly with equivalent exams. the average scores s (on a 100 point scale) for the students can be modeled by
s = 75 - 6 in(t + 1), 0 < t < 12
where t is the time in months.
(a) what was the average score on the original exam?
(b) what was the average score after 4 months?
(c) after how many months was the average score 60?

Step-by-step explanation:

The average scores s (on a 100 point scale) for the students can be modeled by

s = 75 - 6 In(t + 1), 0 < t < 12

where t is the time in months.

a) Since the students were given an exam and then retested monthly with equivalent exams, then,

For the original exam, t = 0

Therefore,

s = 75 - 6 In(0 + 1) = 75 - 6 In1

s = 75 - 6 × 0 = 75

b) the average score after 4 months, t = 4

Therefore,

s = 75 - 6 In(4 + 1) = 75 - 6 In5

s = 75 - 9.66 = 65.34

c) s = 60

Therefore,

60 = 75 - 6 In(t + 1)

6 In(t + 1) = 75 - 60 = 15

In(t + 1) = 15/6 = 2.5

t + 1 = e^2.5 = 12.18

t = 12.18 - 1 = 11.18

t = 11 approximately

$18 was the price of the t-shirt

step-by-step explanation:

walter needs to make at least 5 more cookies but no more than 40. 5 ≤ x ≤ 40

step-by-step explanation:

20 ≤ x + 15 ≤ 55

subtract 15 from all parts

20-15 ≤ x + 15-15 ≤ 55-15

5 ≤ x ≤ 40

this means how many more cookies he has to make

walter needs to make at least 5 more cookies, but no more than 40 cookies; 5 ≤ x ≤ 40