The HCF of two numbers is 9 and their LCM is 252. The sum of numbers is: 

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  1. 108
  2. 78
  3. 90
  4. 99

Answer (Detailed Solution Below)

Option 4 : 99
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Detailed Solution

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Given:

HCF = 9, LCM = 252

Concept:

LCM = Least common multiple (Lease value divisible by all the given numbers)

HCF = highest common factor (Highest value which will exactly divide all the given numbers)

Formula Used:

LCM × HCF = Product of numbers

Calculation:

Let, the numbers be 9x and 9y where x and y are co-prime

According to the question,

9x × 9y = 252 × 9

⇒ xy = 28

Possible values of (x, y) are (1, 28), (28, 1), (4, 7) and (7, 4)

Case 1: For (x, y) is (1, 28) or (28, 1)

The numbers are = (9 × 1) = 9 and (9 × 28) = 252

⇒ Sum of the numbers = (9 + 252) = 261

Case 2: For (x, y) is (4, 7) or (7, 4)

The numbers are = (9 × 4) = 36 and (9 × 7) = 63

⇒ Sum of the numbers = (36 + 63) = 99

∵ 261 is not in options,

∴ Required sum = 99
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