Which form is best for finding ( 99^2 ) easily?
Answer and explanation
Correct answer: \((100-1)^2\)
The correct form is \((100-1)^2\), because 99 is just 1 less than 100. Using \((a-b)^2=a^2-2ab+b^2\), we get \((100-1)^2=10000-200+1=9801\). The expression \((99+1)(99-1)\) equals \(99^2-1\), so it is not equal to \(99^2\). Exam tip: for squaring a number, rewrite it using the nearest convenient multiple of 10 or 100.
Frequently asked questions
What is the correct answer to this question?
\((100-1)^2\)
Why is this the correct answer?
The correct form is \((100-1)^2\), because 99 is just 1 less than 100. Using \((a-b)^2=a^2-2ab+b^2\), we get \((100-1)^2=10000-200+1=9801\). The expression \((99+1)(99-1)\) equals \(99^2-1\), so it is not equal to \(99^2\). Exam tip: for squaring a number, rewrite it using the nearest convenient multiple of 10 or 100.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Algebraic identities.
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