CBSE Class 7 Maths Chapter 15: Finding the Unknown — Assertion & Reason
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The following Assertion and Reason questions are based on Chapter 15: Finding the Unknown from the NCERT Class 7 Mathematics textbook. Each question has four options - read both the Assertion (A) and Reason (R) carefully before selecting your answer.
How to attempt Assertion & Reason questions:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Assertion & Reason Questions
1
Assertion (A): An equation states that two expressions have equal value.
Reason (R): The equality sign balances its left and right sides.
Reason (R): The equality sign balances its left and right sides.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Solutions preserve this equality.
2
Assertion (A): A variable can represent an unknown number.
Reason (R): An expression need not contain an equality sign.
Reason (R): An expression need not contain an equality sign.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both are true, but the expression fact does not explain an unknown.
3
Assertion (A): Subtracting 5 from both sides gives x=7.
Reason (R): The solution of x+5=12 is x=17.
Reason (R): The solution of x+5=12 is x=17.
Answer: (c)
A is true, but R is false. Seven is the solution.
4
Assertion (A): The solution of 3x=15 is x=12.
Reason (R): Dividing both sides by 3 gives x=5.
Reason (R): Dividing both sides by 3 gives x=5.
Answer: (d)
A is false, but R is true. The assertion is false.
5
Assertion (A): Performing the same operation on both sides preserves an equation.
Reason (R): Equal quantities remain equal after equal additions, subtractions, multiplications or allowed divisions.
Reason (R): Equal quantities remain equal after equal additions, subtractions, multiplications or allowed divisions.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. This balance principle justifies solving steps.
6
Assertion (A): The equation x-8=3 is solved by adding 8 to both sides.
Reason (R): The equation 2x=10 is solved by dividing both sides by 2.
Reason (R): The equation 2x=10 is solved by dividing both sides by 2.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both are true, but the second does not explain the first.
7
Assertion (A): An equation must remain balanced by equal operations on both sides.
Reason (R): Adding 4 to only one side preserves equality.
Reason (R): Adding 4 to only one side preserves equality.
Answer: (c)
A is true, but R is false. A one-sided change usually breaks equality.
8
Assertion (A): Division by zero is an allowed equation-solving step.
Reason (R): Division by zero is undefined.
Reason (R): Division by zero is undefined.
Answer: (d)
A is false, but R is true. Such a step is invalid.
9
Assertion (A): Substitution checks a proposed solution.
Reason (R): Replacing the variable should make both sides equal.
Reason (R): Replacing the variable should make both sides equal.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Equality confirms the value satisfies the equation.
10
Assertion (A): The value x=4 satisfies 2x+1=9.
Reason (R): The value x=3 satisfies x+2=5.
Reason (R): The value x=3 satisfies x+2=5.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both are true, but the second equation does not explain the first.
11
Assertion (A): Substitution gives 9 on the left.
Reason (R): The value x=2 satisfies 5x-1=8.
Reason (R): The value x=2 satisfies 5x-1=8.
Answer: (c)
A is true, but R is false. Nine is not eight.
12
Assertion (A): Every equation has exactly one solution.
Reason (R): Some equations have none or many solutions.
Reason (R): Some equations have none or many solutions.
Answer: (d)
A is false, but R is true. Solution count depends on the equation.
13
Assertion (A): Combining like terms can simplify an equation.
Reason (R): It produces an equivalent equation that is easier to solve.
Reason (R): It produces an equivalent equation that is easier to solve.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Equivalent simplification preserves solutions.
14
Assertion (A): The equation 2x+3x=20 has solution x=4.
Reason (R): The equation x/3=5 has solution x=15.
Reason (R): The equation x/3=5 has solution x=15.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both are true, but the second does not explain the first.
15
Assertion (A): Dividing by 4 gives x+2=5.
Reason (R): The equation 4(x+2)=20 has solution x=7.
Reason (R): The equation 4(x+2)=20 has solution x=7.
Answer: (c)
A is true, but R is false. The solution is x=3.
16
Assertion (A): Moving a term across equals changes its sign by magic.
Reason (R): The sign change abbreviates performing the same inverse operation on both sides.
Reason (R): The sign change abbreviates performing the same inverse operation on both sides.
Answer: (d)
A is false, but R is true. Balance operations provide the justification.
17
Assertion (A): A word problem can be modelled by defining an unknown and forming an equation.
Reason (R): The equation translates relationships described in words.
Reason (R): The equation translates relationships described in words.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Solving then answers the original situation.
18
Assertion (A): Consecutive integers can be represented as n and n+1.
Reason (R): Two consecutive integers differ by 1.
Reason (R): Two consecutive integers differ by 1.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both are true, but the difference fact restates rather than independently explains the representation.
19
Assertion (A): Writing n+(n+1)=21 gives n=10.
Reason (R): If two consecutive integers sum to 21, they are 9 and 12.
Reason (R): If two consecutive integers sum to 21, they are 9 and 12.
Answer: (c)
A is true, but R is false. The integers are 10 and 11.
20
Assertion (A): A solution need not be checked in the original equation.
Reason (R): Checking can reveal arithmetic or sign errors.
Reason (R): Checking can reveal arithmetic or sign errors.
Answer: (d)
A is false, but R is true. Verification is an important final step.
❓ Frequently Asked Questions
What is covered in CBSE Class 7 Maths Chapter 15 Finding the Unknown?
This chapter covers all key topics from Finding the Unknown as per CBSE 2026-27 syllabus.
Is this Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 7 board exam preparation covering the complete syllabus.
Are these CBSE Class 7 Maths Assertion & Reason updated for 2026-27?
Yes, all content at eBookPublisher is updated as per the latest 2026-27 CBSE syllabus.
How many chapters are in CBSE Class 7 Maths?
All chapters of CBSE Class 7 Maths are covered at eBookPublisher with free Assertion & Reason for each chapter.
Can I study Finding the Unknown online for free?
Yes, complete Assertion & Reason for Finding the Unknown is available free at eBookPublisher. Study online directly — no download needed.
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