Answer:
-2.25
Explanation:
We have that the mean (m) is equal to 500, the standard deviation (sd) 20
They ask us for P (x <455)
For this, the first thing is to calculate z, which is given by the following equation:
z = (x - m) / sd
We have all these values, replacing we have:
z = (455 - 500) / (20)
z = -2.25