Mental Math Tricks for Students

Question

Squaring a 2-digit number ending in 1

• Take a 2-digit number ending in 1.
• Subtract 1 from the number.
• Square the difference.
• Add the difference twice to its square.
• Add 1.

Example:    61 x 61

1. Subtract 1:61 – 1 = 60
2. Square the difference:60 × 60 = 3600
3. Add the Difference Twice to its Square:3600 + 60 + 60 = 3720
4. Add 1:3720 + 1 = 3721
5. Now you will get!    61 × 61 = 3721

Answer 1

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