Using square root table, find the square root

From the square root table, we have:

$\sqrt{13}=3.606$ and $\sqrt{14}=\sqrt{2} \times \sqrt{7}=3.742$

Their difference is 0.136.

Thus, for the difference of 1 (14 -">−13), the difference in the values of the square roots is 0.136.

For the difference of 0.21, the difference in the values of their square roots is:

$0.136 \times 0.21=0.02856$

$\therefore \sqrt{13.21}=3.606+0.02856 \approx 3.635$