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The LCM of two numbers is 1024 and one o...

The LCM of two numbers is 1024 and one of them is a prime numbers . Find their GCD.

A

3

B

2

C

5

D

7

Text Solution

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The correct Answer is:
To find the GCD (Greatest Common Divisor) of two numbers when their LCM (Least Common Multiple) is given as 1024 and one of the numbers is a prime number, we can follow these steps: ### Step 1: Understand the relationship between LCM and GCD The relationship between LCM and GCD of two numbers \(a\) and \(b\) is given by the formula: \[ \text{LCM}(a, b) \times \text{GCD}(a, b) = a \times b \] ### Step 2: Factorize the LCM We need to factorize the LCM, which is given as 1024. \[ 1024 = 2^{10} \] This means that 1024 is made up of the prime number 2 multiplied by itself 10 times. ### Step 3: Identify the prime number Since one of the numbers is a prime number, and the only prime factor of 1024 is 2, we can conclude that one of the numbers must be 2. ### Step 4: Determine the second number Let’s denote the two numbers as \(a\) and \(b\). We have: - \(a = 2\) (the prime number) - \(b\) is unknown. Using the LCM formula: \[ \text{LCM}(2, b) = 1024 \] Since 2 is a factor of 1024, we can express \(b\) in terms of 1024: \[ b = \frac{\text{LCM}(2, b) \times \text{GCD}(2, b)}{2} \] ### Step 5: Calculate GCD Now, we can use the relationship: \[ \text{GCD}(2, b) = \frac{\text{LCM}(2, b)}{b} \] Since \(b\) must also be a power of 2 (to maintain the LCM as a power of 2), we can express \(b\) as \(2^n\) for some integer \(n\). ### Step 6: Solve for \(n\) Using the LCM of powers of 2: \[ \text{LCM}(2, 2^n) = 2^{\max(1, n)} = 1024 = 2^{10} \] This means \(n\) must be 10, so: \[ b = 2^{10} = 1024 \] ### Step 7: Calculate GCD Now we can find the GCD: \[ \text{GCD}(2, 1024) = 2 \] ### Final Answer Thus, the GCD of the two numbers is: \[ \text{GCD} = 2 \] ---

To find the GCD (Greatest Common Divisor) of two numbers when their LCM (Least Common Multiple) is given as 1024 and one of the numbers is a prime number, we can follow these steps: ### Step 1: Understand the relationship between LCM and GCD The relationship between LCM and GCD of two numbers \(a\) and \(b\) is given by the formula: \[ \text{LCM}(a, b) \times \text{GCD}(a, b) = a \times b \] ...
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Knowledge Check

  • The LCM of two numbers is 1024 and one of them is a prime number. Find their GCD.

    A
    3
    B
    2
    C
    5
    D
    7
  • The LCM of two numbers is 30 and the product of two numbers is 150. Find the HCF

    A
    3
    B
    5
    C
    10
    D
    15
  • The LCM of two numbers is 280 and the ratio of the numbers is 7:8. Find the numbers

    A
    70 and 48
    B
    42 and 48
    C
    35 and 40
    D
    28 and 32
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