At Euclid High School, the number of students taking the [AMC 10](https://artofproblemsolving.com/wiki/index.php/AMC_10) was $60$ in 2002, $66$ in 2003, $70$ in 2004, $76$ in 2005, $78$ and 2006, and is $85$ in 2007. Between what two consecutive years was there the largest percentage increase?
$\text{(A)}\ 2002\ \text{and}\ 2003 \qquad \text{(B)}\ 2003\ \text{and}\ 2004 \qquad \text{(C)}\ 2004\ \text{and}\ 2005 \qquad \text{(D)}\ 2005\ \text{and}\ 2006 \qquad \text{(E)}\ 2006\ \text{and}\ 2007$
We compute the percentage increases:

$\frac{66 - 60}{60} = 10\%$
$\frac{70 - 66}{66} \approx 6\%$
$\frac{76-70}{70} \approx 8.6\%$
$\frac{78-76}{76} \approx 2.6\%$
$\frac{85-78}{78} \approx 9\%$
The answer is $\mathrm{(A)}$. 
In fact, the answer follows directly from examining the differences between each year. The largest differences are $6$ and $7$. Due to the decreased starting number of students between $2002$ and $2003$, that interval will be our answer.
~edited by mobius247