NCERT :GRADE-9: MATHS CHAPTER -1 WORKSHEETS

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Grade 9 Mathematics

Propositions and Their Converses

5 Professional Practice Worksheets • All Questions Carry 1 Mark

πŸ“˜ Practice Series
Test your understanding of propositions, converses, counterexamples, factor-partner reasoning, divisibility, geometry and the converse of the Baudhāyana–Pythagoras theorem.

Important: Every question carries 1 mark. Attempt the questions independently and explain your reasoning wherever required.

Worksheet 1 — Source-Based Questions

15 Questions × 1 Mark = 15 Marks

Read each source carefully and answer the questions that follow.
SOURCE A — PROPOSITIONS

A proposition is a statement that is either true or false. A statement in the form “If X then Y” can also be written as “X implies Y”.

1. What is a proposition? [1]
2. Complete: “If X then Y” can also be written as “X ______ Y”. [1]
3. Is a proposition necessarily true? [1]
SOURCE B — CONVERSE

If a proposition is “If X then Y”, its converse is “If Y then X”.

4. Write the converse of: “If a number is divisible by 6, then it is divisible by 3.” [1]
5. What two parts are interchanged when a converse is formed? [1]
6. Write the converse of: “If x = y, then x² = y².” [1]
SOURCE C — COUNTEREXAMPLE

A proposition may be true while its converse is false. A counterexample is an example that contradicts a stated proposition.

7. What is a counterexample? [1]
8. Give one counterexample to: “Every multiple of 3 is a multiple of 6.” [1]
9. Can one suitable counterexample disprove a universal claim? [1]
SOURCE D — FACTOR PARTNERS

Factors of a number occur in partner pairs. If a number has an odd number of factors, one factor-partner pair contains the same number twice.

10. Give the repeated factor pair of 25. [1]
11. Is 36 a perfect square? [1]
12. How many factors does 49 have? [1]
SOURCE E — PYTHAGOREAN CONVERSE

If a triangle is right-angled, then a² + b² = c². The converse states that if a² + b² = c², then the triangle is right-angled.

13. Write the converse in one sentence. [1]
14. Does 3² + 4² = 5²? [1]
15. Which congruence criterion is used in the chapter's proof of the converse? [1]

Worksheet 2 — Case-Based Questions

15 Questions × 1 Mark = 15 Marks

CASE 1 — PARALLEL LINES

A student writes: “If two lines are parallel, then the corresponding angles formed by a transversal are equal.”

1. What is the converse of this statement? [1]
2. What geometric object cuts the two lines? [1]
3. What type of angles are compared? [1]
CASE 2 — PERFECT SQUARES

A number's factors can be arranged in partner pairs. For a perfect square, the square root forms a repeated factor pair.

4. What is the square root of 81? [1]
5. Write the repeated factor pair of 81. [1]
6. Is 81's number of factors odd or even? [1]
CASE 3 — DIVISIBILITY

Consider the statement: “If n is divisible by 24, then n is divisible by both 4 and 6.”

7. Is 48 divisible by 24? [1]
8. Is 48 divisible by 6? [1]
9. Is 12 a multiple of 24? [1]
CASE 4 — PRIME CLAIMS

The chapter asks students to challenge claims about expressions that are said to produce only prime numbers.

10. Is 2047 prime? [1]
11. What is 2¹¹ − 1? [1]
12. Name the method used to disprove a universal prime claim. [1]
CASE 5 — TRIANGLES
13. What is 5² + 12²? [1]
14. What is the square root of 169? [1]
15. Are 5, 12 and 13 the sides of a right triangle? [1]

Worksheet 3 — Assertion & Reason

15 Questions × 1 Mark = 15 Marks

For each question select the correct option:

A — Both Assertion and Reason are true, and Reason explains Assertion.
B — Both are true, but Reason does not explain Assertion.
C — Assertion is true, but Reason is false.
D — Assertion is false, but Reason is true.
1. Assertion: A proposition is either true or false.
Reason: A proposition is a mathematical statement.
2. Assertion: The converse of “If X then Y” is “If Y then X”.
Reason: The two parts are interchanged.
3. Assertion: A true proposition always has a true converse.
Reason: A proposition and its converse have different forms.
4. Assertion: A counterexample can disprove a universal statement.
Reason: A counterexample contradicts the stated claim.
5. Assertion: Every multiple of 6 is a multiple of 3.
Reason: 6 = 3 × 2.
6. Assertion: Every multiple of 3 is a multiple of 6.
Reason: 9 is a multiple of 3.
7. Assertion: A perfect square has an odd number of factors.
Reason: Its square root forms a repeated factor pair.
8. Assertion: 25 has an odd number of factors.
Reason: Its repeated factor pair is (5,5).
9. Assertion: Congruent triangles have equal areas.
Reason: Congruent triangles have the same size and shape.
10. Assertion: Equal-area triangles must be congruent.
Reason: Different triangles can have the same area.
11. Assertion: If a²+b²=c², the triangle is right-angled.
Reason: This is the converse of the Pythagorean theorem.
12. Assertion: “Y when X” can express the meaning “If X then Y”.
Reason: The chapter gives both forms as equivalent expressions.
13. Assertion: The converse of a proposition may be false.
Reason: The truth of a proposition does not automatically establish its converse.
14. Assertion: 36 has an odd number of factors.
Reason: The factor pair (6,6) occurs for 36.
15. Assertion: The converse of the Pythagorean theorem is true.
Reason: The chapter proves it using construction and SSS congruence.

Worksheet 4 — Multiple Choice Questions

15 Questions × 1 Mark = 15 Marks

Select the most appropriate option. Every question carries one mark.
1. Which is the converse of “If a number is divisible by 8, then it is divisible by 4”?
2. Which number is a counterexample to “Every multiple of 3 is a multiple of 6”?
3. Which number is a perfect square?
4. How many factors does 25 have?
5. Which pair is a factor pair of 35?
6. Which number has exactly three factors?
7. Which expression means “X implies Y”?
8. Which number disproves the claim “All even n make 2ⁿ+1 prime”?
9. What is 7²?
10. Which is the converse of “If x=y, then x³=y³”?
11. Which statement is true?
12. Which pair satisfies the Pythagorean relation?
13. Which criterion is used in the proof of the converse of the Pythagorean theorem?
14. Which statement describes a counterexample?
15. Which number has an odd number of factors?

Worksheet 5 — Mixed Competency & HOTS

15 Questions × 1 Mark = 15 Marks

Answer briefly. Focus on mathematical reasoning rather than lengthy calculations.
1. Write the converse of: “If a quadrilateral is a square, then all its angles are equal.” [1]
2. Give a counterexample to: “Every multiple of 5 is a multiple of 10.” [1]
3. Is the converse of “If it rains, the road is wet” necessarily true? [1]
4. Give one reason why a road may be wet without rain. [1]
5. Write one factor-partner pair of 64 other than (1,64). [1]
6. Is 64's number of factors odd or even? [1]
7. What is the repeated factor pair of 64? [1]
8. Write the converse of: “If n is divisible by 60, then n is divisible by 5 and 12.” [1]
9. Is 60 divisible by both 5 and 12? [1]
10. Express “a number is divisible by 3” using the digit-sum condition. [1]
11. What is the sum of the digits of 123? [1]
12. Is 123 divisible by 3? [1]
13. For sides 9, 40 and 41, calculate 9²+40². [1]
14. Does 9²+40² equal 41²? [1]
15. Based on the converse of the Pythagorean theorem, what type of triangle has sides 9, 40 and 41? [1]

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