Question

Use technology or a z-score table to answer the question. The weights of boxes of rice produced at a factory are normally distributed with a mean of 24 ounces and a standard deviation of 1.3 ounces. Consider a shipment of 1200 boxes of rice. How many of the boxes will weigh 25 ounces or less?
192
265
935
1008

Answer 1

935 of the boxes will weigh 25 oz or less.

The z-score for this value is 
$z=\frac{25-24}{1.3}=\frac{1}{1.3} = 0.77$

Looking this up in a z-table (http://www.z-table.com) we see that the probability of something being less than or equal to this value (the area under the curve to the left) is 0.7794.  

Multiply this probability by the number of items:
0.7794(1200) = 935.28 ≈ 935.