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What is the easy way to multiply two numbers ending with 5?

Take a few examples. Say25*35 or35*75 or45*95.

Mathematics
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Question added by Vinod Jetley , Assistant General Manager , State Bank of India
Date Posted: 2014/08/30
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Vinod Jetley
by Vinod Jetley , Assistant General Manager , State Bank of India

Take75*25, for example. Add the numbers and divide by2. We get50, square it, we get2500.

Take the difference of two numbers and divide by2. We get25, square it, we get625.

2500-625=1875 is the answer.

(a+b)*(a-b)=a^2-b^2

In the above example a=50, b=25

so,75*25=50^2-25^2

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