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What is the HCF of 18 and 28?

52. What is the HCF of 18 and 28?

1. 8
2. 10
3. 2
4. 6

Answer

The correct answer is: D) 6

Explanation

The explanation is:

• 18 has two prime factors: 2¹ and 3² (since 18 = 2 * 3 * 3).
  28 have two prime factors: 2² and 7¹ (since 28 = 2 * 2 * 7).
• Now, from both numbers, take the least power of each prime factor.
  The smallest power of 2 is 2¹.
  The smallest power of 3 is 3¹.
  There is no common prime factor of 7 in both numbers.
• To calculate the HCF, multiply all of the common prime factors together.
  HCF = 2^1 * 3^1 = 2 * 3 = 6

Therefore, the HCF of 18 and 28 is 6.