Question 1199260
the mean is 522.7 kg
the variance is 100 square kg.
the standard deviation is the square root of the variance = 100 kg
raw score you want to test against is 521 kg
z-score formula is z = (x - m) / s
x is the raw score
m is the mean
s is the standard deviation.
formula becomes z = (521 - 522.7) / 100 = -.017
area to the left of a z-score of -.017 = .493218 rounded to 6 decimal places.
that's the probability that the weight of concrete poured into a mold is less than 521 kg.
that's equal to 49.32% rounded to 2 decimal places.