[tex]\mathbb P(40<X<44)=\mathbb P\left(\dfrac{40-42}2<\dfrac{X-42}2<\dfrac{44-42}2\right)=\mathbb P(-1<Z<1)[/tex]
In a normal distribution, about 68% of it lies within one standard deviation of the mean, so [tex]\mathbb P(-1<Z<1)\approx0.68[/tex].
So if 68% of the population is 450, then there must be about 662 total values.
