Dear Math Helper, I work in construction and am pretty good in math, especially with fractions, so I didn't think I would ever have to write to you. But this one has got me stumped. Last week I bought two boxes of nails, each from a different manufacturer. I poured the nails from one box into my left pocket and the other into my right. I started to use the ones in my left pocket, but they kept breaking and bending. I will never use them again. But here's my problem. I don't remember which box they came from. I contacted both manufacturers and "Manufacturer A" said their boxes have a mean of 205.4 nails and a standard deviation of 1.8 nails. "Manufacturer B" said their boxes have a mean of 190.6 nails and a standard deviation of 3.3 nails. Both said their number of nails is normally distributed. I counted the nails from my left pocket, including the used ones, and got 198. This is 7.4 nails less than Manufacturer A and 7.4 nails more than Manufacturer B. So I guess the standard deviation comes into play, but I don't know how. Please explain which manufacturer most likely made these defective nails. Sincerely, Stumped Builder