<p>I’m not a math geek, but I’ll give it a try. What you’re calculating in the case of a senior who’s taken, say four years of 7 courses X 4 quarters with all Bs is:</p>
<p>336.0 (grade points)/112 (individual quarterly grades)=3.00[0]</p>
<p>The single significant digit in 336.0 is correct because no decimal places have been added.</p>
<p>And as a footnote, even if the 112 were a number below 100, it would still, as a whole number, have an unlimited number of possible significant digits. There’s no error measurement; the kid took exactly 24 courses and received exactly 112 grades. So schools could report scores to 4 significant digits.</p>