Telangana SCERT Solution Class IX (9) Math Chapter 1 Real Numbers Exercise 1.2
(1.) Classify the following numbers as rational or irrational.
(i) √27
Solution: √27 = √9 x √3
= 3√3
Therefore, √27 is an irrational number.
(ii) √441
Solution: √441 = √3 x √147
= √3 x √3 x √49
= √3 x √3 x √7 x √7
= 3 x 7
= 21
Therefore √441 is a rational number.
(iii) 30.232342345…
Solution: It is an irrational number because the above given number is a non-terminating decimal number and non-recurring decimal number.
(iv) 7.484848…
Solution: the above mentioned number is rational number because it is a non terminating decimal number but it can be expressed in fractions. since it is a recurring decimal.
(v) 11.2132435465
Solution: The above mentioned number is a non-terminating and non-recurring decimal number hence it is an irrational number.
(vi) 0.3030030003…
Solution: The above given number is non-terminating and non-recurring hence it is an irrational number.
(2.) Give four examples for rational and irrational numbers?
Solution: For example of rational number are,
1, 2, 2/3, 4/5
Four example of an irrational number are,
√2, √3, √5, π (pi).
(4.) Find two irrational numbers between 0.7 and 0.77
Solution: Two irrational numbers between 0.7 and 0.77 are
i) 0.745689…,
ii) 0.732145
[Any random non-recurring and non terminating number between the given number can be treated as irrational numbers].
(5.) Find the value of √5 upto 3 decimal places
Solution: Using long division method to find out the value of √5
Step 1: You take the values to be calculated and put 3 pair of zero in it after a decimal point.
Step 2: Now take a number lower than the given number and multiply it with itself. so that the result is also lower then the given number in this case it is 2.
Step 3: Put the number in quotient and dividend and subtracts the result from the divisor.
Step 4: Put the pair of zeros beside the remainder, and add the quotient with the dividend and put it on the next dividend in this case its 2 + 2 = 4.
Step 5: Now, calculate and chose a number that when put beside the dividend and multiplied with itself gives a number that is lower than the total remainder or the new devisor in this case its 42 x 2 = 84 < 100
Step 6: Follow the above steps until you get upto.
(8.) Find atleast two irrational numbers between 2 and 3.
Solution: Given,
a = 2, b = 3
To find irrational number between 2 and 3 √ab should not be a perfect square.
∵ ab = 2 x 3 = 6 [Not a perfect square]
∴ an irrational number between 2 and 3 is √6.
Another method ->
22 = 4 and 32 = 9
so the numbers between 4 and 9 are not perfect squares hence the square root of those numbers are irrational and they lay between 2 and 3.
∴ √5, √7 are also two irrational numbers between 2 and 3.
(9.) State whether the following statements are true or false. Justify your answers.
(i) Every irrational number is a real number.
Ans. True.
(ii) Every rational number is a real number.
Ans. True.
(iii) Every real number need not be a rational number
Ans. True.
(iv) √n is not irrational if n is a perfect square.
Ans. True.
(v) √n is irrational if n is not a perfect square.
Ans. True.
(vi) All real numbers are irrational.
Ans. False.
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