Mathematics

Substitution

In this Class 9 Mathematics topic, students learn how to replace a variable with a known number or algebraic expression and then simplify the result correctly. The topic builds understanding of substitution in algebraic expressions, formulas, and equations, including the careful use of brackets, signs, powers, and the order of operations. As part of the Common Questions chapter, it also helps students identify typical calculation errors and check whether their final answer is reasonable.

Easy · Level 1 · 2 questions

Practice questions

01If \(y=4\), what is the value of \(y^2\)?

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Answer and explanation

Correct answer: C. \(16\)

\(y^2\) means \(y\times y\). Substituting \(y=4\), we get \(y^2=4^2=4\times4=16\). Option 8 equals \(2y\), not \(y^2\). In such questions, substitute the given value first and then evaluate the power.

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02If \(u=7\) and \(v=2\), what is the value of \(u-v\)?

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Answer and explanation

Correct answer: B. 5

Substituting the given values in \(u-v\) gives \(7-2=5\), so option B is correct. Option A results from addition, \(7+2=9\), option C results from multiplication, \(7\times2=14\), and option D is an incorrect subtraction. In an exam, carefully preserve the order of terms because \(u-v\) and \(v-u\) generally have different values.

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Substitution

Practice questions

01If \(y=4\), what is the value of \(y^2\)?यदि \(y=4\) है, तो \(y^2\) का मान क्या होगा?

02If \(u=7\) and \(v=2\), what is the value of \(u-v\)?यदि \(u=7\) और \(v=2\) हों, तो \(u-v\) का मान क्या होगा?

Analytics choices

01If \(y=4\), what is the value of \(y^2\)?

02If \(u=7\) and \(v=2\), what is the value of \(u-v\)?