Question

Given a population of 5000 score with mean μ=86 and σ=10. How many scores are below 56?

Answer 1

$$P(X<56)=P(Z<\dfrac{56-86}{10})$$

$$=P(Z<-3)\approx0.00135$$

$$0.00135\cdot 5000=7$$

7 scores are below 56.