If the square root of 170 is really all you want, use a calculator's square root operator to find this root. According to my calculator, the root is 13.04, to 2 decimal place accuracy.
Note that 169 is just below 170 and that the sqrt of 169 is 13; 196 is the square of 14. Thus, the square root of 170 must lie between 13 and 14, and must be closer to 13 than to 14 because 170 is much closer to 169 than is 196.
In the old days, schools taught how to find square roots without a calculator.
