We find a mean of 1048 washers per box with a standard devia

We find a mean of 1048 washers per box, with a standard deviation of 212. What is the probability of finding 820 or less, or 1398 or more?   show work plz

Solution

Mean = 1048

Standard deviation = 212

Convert X to Z we have,

Z = X-Mu / Sigma

Therefore,

P(X<=820) = P(Z<= (820 - 1048 )/212 = p(z<=-1.08) = .1401

p(x>1398) = p(z > 1398 - 1048/212) = p(z>1.651 ) = 1-.9505 = .0495