Squaring Numbers Ending in 5: A Simple Trick

Squaring numbers can be a tedious task, especially for larger numbers. But what if I told you there’s a simple trick to square any number ending in 5? This method involves breaking down the number and applying a specific formula, making the calculation much faster and easier.

The Trick

Here’s how it works:

1. Isolate the tens digit: Take the number you want to square and remove the ‘5’. For example, if you’re squaring 35, you’d isolate the ‘3’.
2. Multiply the tens digit by its successor: Multiply the isolated tens digit by the next consecutive number. In our example, you’d multiply 3 by 4, which equals 12.
3. Append ’25’: Finally, add ’25’ to the result from step 2. So, 12 plus 25 equals 37.

Therefore, the square of 35 is 1225.

Example

Let’s try another example: squaring 65.

1. Isolate the tens digit: 6
2. Multiply the tens digit by its successor: 6 * 7 = 42
3. Append ’25’: 42 + 25 = 4225

So, the square of 65 is 4225.

Why Does This Work?

This trick works because of the algebraic expansion of (10a + 5)², where ‘a’ represents the tens digit. Expanding this expression gives us:

(10a + 5)² = 100a² + 100a + 25

Notice that the first two terms can be factored out as 100a(a + 1). This aligns with the steps we followed in the trick. The final term, 25, is appended to the result as the last step.

Applications

This simple trick can be incredibly useful for:

• Mental Math: Quickly calculate squares of numbers ending in 5 without a calculator.
• Mathematical Concepts: Understand the algebraic principles behind squaring numbers.
• Problem Solving: Solve math problems involving squares of numbers ending in 5 more efficiently.

Conclusion

Squaring numbers ending in 5 doesn’t have to be daunting. By following this simple trick, you can easily and quickly calculate their squares. This method is a great tool for mental math, understanding mathematical concepts, and solving problems more effectively.