Suppose the final exam scores in a large class is symmetric mound shaped with a mean of 70 points and standard deviation of 10 points. The percentage of students in the class who receive more than 60 points is approximately

Answer 1

Use z-scores.

Formula:
z = (x - mean)/sd

x = 60
mean = 70
sd = 10

Substitute into the formula and find z. Use a z-distribution table to find the probability. Convert to a percent.

I hope this will help get you started.

Answer 2

60% is 70%-10% (1 standard deviation).

Look up a normal distribution table (or
http://www.mathsisfun.com/data/standard-normal-distribution-table.html
)
to find that at Z=1 (1 standard deviation) below mean is (0.5)-0.3413=0.1587
So 15.87% of the class has (70-10)=60% or less. So how many are above 60?