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Question

How to find the square roots of a five digit number 16244

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Solution

Two find the square root of any five digit perfect square number:

Step-1: Look at the magnitude of the “hundreds number” (the numbers preceding the last two digits) and find the largest square that is equal to or less than the number. This is the 1st part of the answer.

Step-2: Now, look at the last (unit’s) digit of the number. If the number ends in

0 : then the ending digit of the answer is a 0

1 : then the ending digit of the answer is 1 or 9.

4 : then the ending digit of the answer is 2 or 8.

5 : then the ending digit of the answer is a 5.

6 : then the ending digit of the answer is 4 or 6.

9 :then the ending digit of the answer is 3 or 7.

Step 3:

To determine the right answer from 2 possible answers (other than 0 and 5), mentally multiply the findings in step-1 with its next higher number. If the left extremities (the numbers preceding the last two digits) are greater than the product, the right digit would be the greater option (9,8,7,6) and if left extremities are less than the product, the right digit would be the smaller option (1,2,3,4).

Let me enlighten you with a trick, assuming you’re not looking for the old school way.

Step-1: Look at the magnitude of the “hundreds number” (the numbers preceding the last two digits) and find the largest square that is equal to or less than the number. This is the 1st part of the answer.

Step-2: Now, look at the last (unit’s) digit of the number. If the number ends in a:

0 -> then the ending digit of the answer is a 0

1 -> then the ending digit of the answer is 1 or 9.

4 -> then the ending digit of the answer is 2 or 8.

5 -> then the ending digit of the answer is a 5.

6 -> then the ending digit of the answer is 4 or 6.

9 -> then the ending digit of the answer is 3 or 7.

To determine the right answer from 2 possible answers (other than 0 and 5), mentally multiply the findings in step-1 with its next higher number. If the left extremities (the numbers preceding the last two digits) are greater than the product, the right digit would be the greater option (9,8,7,6) and if left extremities are less than the product, the right digit would be the smaller option (1,2,3,4).

Let me illustrate the trick with an example:

Square root of 13689 (√13689) = ?

1. Focusing 136; the highest square in it is 11 (since, 112 = 121 and 122 = 144).

2. The last digit of the number is 9 so; the ending digit of the answer would be 3 or 7.

11 times its next higher number (12) is 132 and 136 is greater than 132, so the right digit of the answer would be 7.

So, the final answer is 117.

Here 16244 is not a perfect square number.So we cannot use this trick.




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