Question 1157340
z=(x-mean)/sd
=(2997.5-3000)/2
that is -2.5/2=-1.25
probability of z < -1.25 is 0.1056
so the number of lengths fewer than 2997.5 mm long is the product of the prob and the number 500 or 52.8. I would expect 53 on average to be in that group.