Question

Which of the following numbers would have the digit 6 at its unit place?

• A. ${23}^2$
• B. ${45}^2$
• C. ${54}^2$
• D. ${129}^2$

Answer 1

The correct option is C ${54}^2$

Digit at units place of any square number is equal to the digit at units place of the square of the unit digit of that number.
Unit digit of ${23}^2$= Unit digit of $3^2=9$
Unit digit of ${45}^2$= Unit digit of $5^2=5$
Unit digit of ${54}^2$= Unit digit of $4^2=6$
Unit digit of ${129}^2$= Unit digit of $9^2=1$

So, ${54}^2$ will have the digit 6 at its unit place.