Question

Which of the following is the correct expression of $24\times 26$?

• A. ${24}^2-1$
• B. ${26}^2-1$
• C. ${25}^2-1$
• D. ${25}^2+1$

Answer 1

The correct option is C ${25}^2-1$

Product of two consecutive even numbers is equal to the square of the odd number between them minus 1.
$24\times 26={25}^2-1$

This can also be proved as shown below:
$24\times 26=(25-1)(25+1)$
$24\times 26={25}^2-1^2$
$24\times 26={25}^2-1$