[pfnm]

Here are voltage measurements:
1.37, 1.84, 1.35, 1.47, 1.10, 1.73, 1.54, 1.08 (all in mv)

I've found the S/N (as the mean over the std deviation) as 5.30.

But the question asks:

How many measurements would have to be averaged to increase S/N to 10?

I have the answer but I don't know how it's found. The question is from Skoog, Instrumental Analysis, 4th ed, chapter 4.