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Which of the following cannot be the LCM when HCF of two numbers is 15, and each number is greater than 15 and less than 120.


1. 90
2. 225
3. 360
4. 150

1 Answer

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Best answer
Correct Answer - Option 3 : 360

Given:

HCF of two numbers id 15 and each number is greater than 15 and less than 120

Formula used:

Product of numbers = HCF × LCM

Calculation:

Let the numbers be 15x and 15y, where x and y are co-prime

Product of numbers = 15x × 15y

⇒ 225xy = 15 × LCM

⇒ LCM = 225xy/15

⇒ LCM = 15xy

By checking options

Option 1

LCM = 15xy = 90

⇒ xy = 6 = 2 × 3

2 and 3 are co-prime

Numbers are 30 and 45

LCM = 90 is possible

Opton 2

LCM = 15xy = 225

⇒ xy = 15 = 3 × 5

3 and 5 are co-prime

Numbers are 45 and 75

LCM = 225 is possible

Option 3

LCM = 15xy = 360

⇒ xy = 24 = 3 × 8

3 and 8 are co-prime

Numbers are 45 and 120, Numbers should be less than 120.

Hence, LCM = 360 is not possible for the given conditions

Option 4

LCM = 15xy = 150

⇒ xy = 10 = 2 × 5

2 and 5 are co-prime

Numbers are 30 and 75

LCM = 150 is possible

∴ LCM cannot be 360 

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