LCM and HCF
 Find the least number which when divided by 12, 15, 20 and 24 leaves the same remainder 2 in each case ?

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Required number = LCM of (12, 15, 20, 24) + 2
Correct Option: A
Required number = LCM of (12, 15, 20, 24) + 2
= 120 + 2 = 122
 If there number are 2a, 5a, and 7a, what will be their LCM?

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Required LCM = a x 2 x 5 x 7
Correct Option: A
Required LCM = a x 2 x 5 x 7 = 70a
 What will be the HCF of ( 2 x 3 x 7 x 9 ), ( 2 x 3 x 9 x 11 ) and ( 2 x 3 x 4 x 5 )?

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∴ Required HCF = Product of common prime factors having least powers
Correct Option: C
Given factors
2 x 3 x 7 x 9; 2 x 3 x 9 x 11; 2 x 3 x 4 x 5
∴ Required HCF = Product of common prime factors having least powers = 2 x 3
 Find the LCM of 1/3, 2/9, 5/6 and 4/27.

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LCM of fractions = (LCM of numerators) / (HCF of denominators)
Correct Option: C
We known that,
LCM of fractions = (LCM of numerators) / (HCF of denominators)
∴ Required LCM = (LCM of 1, 2, 5, and 4) / (HCF of 3, 9, 6 and 27)
∴ = 20/3
 Find the LCM of 2/3, 3/5, 4/7 and 9/13.

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Required LCM = (LCM of 2, 3, 4, 9) / (HCF of 3, 5, 7, 13)
Correct Option: A
Required LCM = (LCM of 2, 3, 4, 9) / (HCF of 3, 5, 7, 13)
= (4 x 9)/1
= 36