Right, this should be bloody simple for you - I'm have no problems with these calculations just this particular question doesn't really make sense...
Terry the toymaker is making cubic blocks and packing them in a box. The sides of the cubes vary randomly and have a mean of 66mm and standard error or 1mm. The inside width of the box also varies with a mean of 400mm with a standard error of 2mm.
a) The blocks fit in a row across the box. Estimate how many blocks will fill a row and calculate the mean size of any gap.
b) Calculate the standard deviation of the gap left in your row of blocks.
c) Explain what your answers to 3a and 3b above imply for Terry the toymaker?
So yeah, my mind has gone a bit numb. Cheers.