Find the square root of 42.25. 

The square root of a decimal number can be calculated by using the estimation method or the long division method.

Let's find the square root of 42.25 step by step.

Step 1: To find the square root of a decimal number we put bars on an integral part (i.e., 42) of the number in the usual manner. And place bars on the decimal part (i.e., 25) on every pair of digits beginning with the first decimal place. We get $\overline{42}.\overline{25}$.

Step 2: Now proceed in a similar manner. The left most bar is on 42 and 6² < 42 < 7². Take this number as the divisor and the number under the left-most bar as the dividend, i.e., 42. Divide and get the remainder (As per Fig:1).

Step 3: The remainder is 6. Write the number under the next bar (i.e., 25) to the right of this remainder, to get 625 (As per Fig:1).

Step 4: Double the divisor and enter it with a blank on its right. Since 25is the decimal part so put a decimal point in the quotient (As per Fig:1). 

Step 5: We know 125 × 5= 625, therefore, the new digit is 5. Divide and get the remainder (As per Fig:1). 

Step 6: Since the remainder is 0 and no bar left, therefore $\sqrt{42.25}=6.5$.