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8th Class Mathematics Algebraic Expressions Question Bank Algebraic Expressions and Identities

  • question_answer
    Using the identity \[{{a}^{2}}-{{b}^{2}}=(a+b)\,(a-b),\]valuate\[24.7\times 25.3\].

    A)  \[624.91\]                          

    B)  \[642.91\]          

    C)  \[624.19\]          

    D)         \[642.19\]          

    Correct Answer: A

    Solution :

    \[24.7\times 25.3=(25-0.3)\,(25+0.3)\] \[={{25}^{2}}-{{(0.3)}^{2}}\] \[=625-0.09=624.91\]


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