The number of nails of a given length is normally distributed with a mean length of 5 in. and a standard deviation of 0.03 in. In a bag containing 120 nails, how many nails are more than 5.03 in. long?

a. about 38 nails

b. about 41 nails

c. about 16 nails

d. about 19 nails

The length 5.03 inches belonged to the first range of span of standard deviation. The probability of having length below 5.03 is equal to 68%. The pro probability of having length above 5.03 therefore is (100-68) / 2 or equal to 16%. 16% of 120 nails given is 19.2 or D. about 19 nails.