Real Number
Previous Year Solved Questions 2020
Q1: The HCF and the LCM of 12, 21 and 15 respectively, are (CBSE 2020)
(a) 3, 140 (b) 12, 420 (c) 3, 420 (d) 420, 3
(a) 3, 140 (b) 12, 420 (c) 3, 420 (d) 420, 3
View Answer
Ans: (c) 3, 420
Prime factorisation:
12 = 2² × 3
21 = 3 × 7
15 = 3 × 5
HCF = 3 (only common factor)
LCM = 2² × 3 × 5 × 7 = 4 × 3 × 5 × 7 = 420
Prime factorisation:
12 = 2² × 3
21 = 3 × 7
15 = 3 × 5
HCF = 3 (only common factor)
LCM = 2² × 3 × 5 × 7 = 4 × 3 × 5 × 7 = 420
Q2: The LCM of two numbers is 182 and their HCF is 13. If one of the numbers is 26, find the other. (CBSE 2020)
View Answer
Ans: 91
Using HCF × LCM = Product of numbers
13 × 182 = 26 × other number
2366 = 26 × other number
Other number = 2366 ÷ 26 = 91
Using HCF × LCM = Product of numbers
13 × 182 = 26 × other number
2366 = 26 × other number
Other number = 2366 ÷ 26 = 91
Q3: Given that HCF(135, 225) = 45, find LCM(135, 225). (CBSE 2020)
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Ans: 675
Using HCF × LCM = Product of numbers
45 × LCM = 135 × 225
LCM = (135 × 225) ÷ 45
135 × 225 = 30375
30375 ÷ 45 = 675
Using HCF × LCM = Product of numbers
45 × LCM = 135 × 225
LCM = (135 × 225) ÷ 45
135 × 225 = 30375
30375 ÷ 45 = 675