Class 10 Maths NCERT Solutions Chapter 1 Real Numbers
Class 10 Maths Real Numbers Exercise 1.1
Question 1
Use Euclid’s division algorithm to find the HCF of :
(i) 135 and 225 (ii) 196 and 38220 (iii) 867 and 255
Solution:
(i) 135 and 225
Method 1:
Method 2:
(ii) 196 and 38220
Method 1:
Method 2:
(iii) 867 and 255
Method 1:
Method 2:
Question 2:
Show that any positive odd integer is of the form 6q + 1, or 6q + 3, or 6q + 5, where q is some integer.
Solution:
Method 1:
Method 2:
Question 3:
An army contingent of 616 members is to march behind an army band of 32 members in a parade. The two groups are to march in the same number of columns. What is the maximum number of columns in which they can march?
Solution:
Method 1:
Method 2:
Question 4:
Use Euclid’s division lemma to show that the square of any positive integer is either of the form 3m or 3m + 1 for some integer m.
[Hint : Let x be any positive integer then it is of the form 3q, 3q + 1 or 3q + 2. Now square each of these and show that they can be rewritten in the form 3m or 3m + 1.]
Solution:
Method 1:
Method 2:
Question 5:
Use Euclid’s division lemma to show that the cube of any positive integer is of the form 9m, 9m + 1 or 9m + 8.
Solution:
Method 1:
Method 2:
Class 10 Maths Real Numbers Exercise 1.2
Question 1:
Express each number as a product of its prime factors:
(i) 140 (ii) 156 (iii) 3825 (iv) 5005 (v) 7429
Solution:
(i) 140
Method 1:
Method 2:
(ii) 156
Method 1:
Method 2:
Question 2:
Find the LCM and HCF of the following pairs of integers and verify that LCM × HCF = product of the two numbers.
(i) 26 and 91 (ii) 510 and 92 (iii) 336 and 54
Solution:
(i) 26 and 91
Method 1:
Method 2:
(ii) 510 and 92
Method 1:
Method 2:
(iii) 336 and 54
Method 1:
Method 2:
Question 3:
Find the LCM and HCF of the following integers by applying the prime factorisation method.
(i) 12, 15 and 21 (ii) 17, 23 and 29 (iii) 8, 9 and 25
Solution:
(i) 12, 15 and 21
Method 1:
(ii) 17, 23 and 29
Method 1:
Method 2:
(iii) 8, 9 and 25
Method 1:
Method 2:
Question 4:
Given that HCF (306, 657) = 9, find LCM (306, 657).
Solution:
Method 1:
Method 2:
Question 5:
Check whether 6n can end with the digit 0 for any natural number n.
Solution:
Method 1:
Method 2:
Question 6:
Explain why 7 × 11 × 13 + 13 and 7 × 6 × 5 × 4 × 3 × 2 × 1 + 5 are composite numbers.
Solution:
Method 1:
Method 2:
Question 7:
There is a circular path around a sports field. Sonia takes 18 minutes to drive one round of the field, while Ravi takes 12 minutes for the same. Suppose they both start at the same point and at the same time, and go in the same direction. After how many minutes will they meet again at the starting point?
Solution:
Method 1:
Method 2:
Class 10 Maths Real Numbers Exercise 1.3
Question 1.
Prove that √5 is irrational.
Solution:
Method 1:
Method ii:
Question 2.
Show that 3 + √5 is irrational.
Method 1:
Method 2:
Question 3.
Prove that the following are irrational.
Solution:
(i)1/√2
Method 1:
Method 2:
(ii) 7√5
Method 1:
Method 2:
(iii) 6 + √2
Method 1:
Method 2:
Class 10 Maths Real Numbers Exercise 1.4
Question 1:
Without actually performing the long division, state whether the following rational numbers will have a terminating decimal expansion or non-terminating repeating decimal expansion:
Solution:
Alternatively:
Alternatively:
Alternatively:
Alternatively:
Alternatively:
Alternatively:
(vii)
Alternatively:
(Viii)
Alternatively:
(ix)
Alternatively:
(x)
Alternatively:
Question 2.
Write down the decimal expansions of those rational numbers in the question 1, which have terminating decimal expansions.
Solution:
Alternatively:
Question 3:
The following real numbers have decimal expansions as given below. In each case, decide whether they are rational or not. If they are rational and of the form 
(i) 43. 123456789
(ii) 0.120120012000120000…
(iii) 43.
Solution:
Alternatively:
Alternatively:
Alternative:
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