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Question

The HCF and LCM of two numbers are 12 and 360. If the numbers differ by 12, their sum will be :

This question was previously asked in
CUET PG 2026 Agri-Business Management Question Paper (25-Mar-2026) (Shift 2)
The correct answer is
132

Problem Setup: HCF, LCM, and Difference Given

We are given the Highest Common Factor (HCF) and Least Common Multiple (LCM) of two numbers, along with their difference. We need to find their sum.

  • HCF = 12
  • LCM = 360
  • Difference between the numbers (let them be $a$ and $b$, so $a - b$) = 12

Key Relationship: Product of Numbers

A fundamental property states that the product of two numbers ($a \times b$) is equal to the product of their HCF and LCM.

Calculation:

$a \times b = \text{HCF} \times \text{LCM}$

$a \times b = 12 \times 360$

$a \times b = 4320$

Finding the Sum Using Algebraic Identity

We can use the algebraic identity relating the sum ($a+b$), difference ($a-b$), and product ($ab$) of two numbers:

$(a+b)^2 = (a-b)^2 + 4ab$

Substitute the known values (difference = 12, product $ab = 4320$):

$(a+b)^2 = (12)^2 + 4 \times (4320)$

$(a+b)^2 = 144 + 17280$

$(a+b)^2 = 17424$

Calculating the Sum

To find the sum ($a+b$), take the square root of both sides:

$a+b = \sqrt{17424}$

$a+b = 132$

Thus, the sum of the two numbers is 132.

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Important Questions from Number System (Notes)

  1. Which number system uses only digits 0 and 1?
  2. The sum of the digits of a 2-digit number is 12. When the digits of the number are interchanged, the number becomes 15 more than twice the original number. The original number is:
  3. What is the least number which, when divided by 7, 12 and 15 leaves 1 as the remainder in each case?
  4. If $\frac{1}{9!} + \frac{1}{10!} = \frac{x}{11!}$, then the value of x is:
  5. What will be the output, if we compute the 9's complement of the decimal number 782.54?
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