Page 13 - Mathematics Class - IX

Viva-Voce

1. Are all irrational numbers real numbers?
Ans. Yes! All irrational numbers are real numbers.
2. Are the square roots of all positive integers irrational?

Ans. No, 4 = 2, 9 = 3, etc. are all rational numbers.
3. Give one example of irrational number.
Ans. 3.21463210011249...
4. What are surds?
Ans. A surd is a radical that cannot be evaluated precisely. For example, 2, 3, 5, ...etc.

5. State Pythagoras Theorem.
Ans. In a right-angled triangle, the sum of the squares of the two sides is equal to the square of its hypotenuse
(H = P + B ).
2
2
2
6. Write 100 as the sum of squares of two natural numbers.
Ans. 100 = 36 + 64
100 = 6 + 8 2
2
or
10 = 6 + 8 2
2
2

MCQs

1. The rationalizing factor of 23 is

a) 2 b) 3 c) 3 d) None of these
2. The set of collection of rational and irrational numbers is called

a) Integers b) Natural numbers c) Whole numbers d) Real numbers

3. The mixed surd of 18 is

a) 23 b) 32 c) 9 d) 62

4. The sum of 3+ 5 and 3− 5 is

a) 11 b) 62 5+ c) 6 d) 62 5−

5. The rationalizing factor of 62 7− is

a) 62 7+ b) 62 7− c) 6 + 7 d) 6 − 7

Answers: 1. c) 3 2. d) Real numbers 3. b) 32

4. c) 6 5. a) 62 7+

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