The number of nails in a 5 lb box is normally distributed with a mean of 325 nails and a standard deviation of 15 nails.

suppose that 1200 different 5 lb boxes are in a warehouse.

about how many boxes contain more than 340 nails?

170

192

340

384

By 68-95-99 rule, it can be said that 68% of the population values lie within the one standard deviation away from the mean.

Probability less than or equal to 340 = 0.5 + 0.68/2 = 0.84
Probability greater than 340 = 1 - 0.84 = 0.16
Hence, number of boxes = 1200 x 0.16 = 192

There are 192 boxes that contain more than 340 nails.