The answer for the square has either 3 or 4 digits.
The last 2 digits of the answer is 25.
METHOD
Step 1. Add 1 to the tens digit.
Step 2. Multiply the sum rom Step 1 by the original tens digit value giving the leftmost digits for the square.
Step 3. Combine the product from Step 2 with 25.
| Number | Tens digit | Step 1 | Step 2 | Step 3 |
|---|---|---|---|---|
| 15 x 15 | 1 | 1 + 1 = 2 | 2 x 1 = 2 | 2 25 |
| 25 x 25 | 2 | 2 + 1 = 3 | 3 x 2 = 6 | 6 25 |
| 35 x 35 | 3 | 3 + 1 = 4 | 4 x 3 = 12 | 12 25 |
| 45 x 45 | 4 | 4 + 1 = 5 | 5 x 4 = 20 | 20 25 |
| 55 x 55 | 5 | 5 + 1 = 6 | 6 x 5 = 30 | 30 25 |
| 65 x 65 | 6 | 6 + 1 = 7 | 7 x 6 = 42 | 42 25 |
| 75 x 75 | 7 | 7 + 1 = 8 | 8 x 7 = 56 | 56 25 |
| 85 x 85 | 8 | 8 + 1 = 9 | 9 x 8 = 72 | 72 25 |
| 95 x 95 | 9 | 9 + 1 = 10 | 10 x 9 = 90 | 90 25 |
