100 students take a course pass/fail. if they pass they get 4 points towards their gpa, if they fail they get 0. if 90 students pass, what is the mean and standard deviation (to 1 decimal) of the points earned?

mean:

standard deviation:

Given:
100 students:
pass = + 4
fail =+ 0

90 students passed: 90 * 4 = 360
10 students failed: 10 * 0 = 0

mean: 360 / 100 = 36

standard deviation: 
36 - 4 = 32 ⇒ 32² = 1,024 * 90 = 92,160
36 - 0 = 36 ⇒ 36² = 1,296 * 10 = 12,960

92,160 + 12,960 = 105,120
105,120 / 100 = 1,051.20 ⇒ variance

Standard deviation = √1,051.20 = 32.42