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Difficulty: 2/102025 IOQM 2025 (Q27)

What is the sum of all prime numbers between and ?

Options:

  • A.

    61

  • B.

    63

  • 60

  • D.

    62

Guide / Hint

Hint 1: List all prime numbers in the range .

Hint 2: The primes are 11, 13, 17, and 19.

Hint 3: Add these four prime numbers together: .

Solution

Step 1: List all integers strictly between and : .

Step 2: Identify the prime numbers from this list:

  • (prime)

  • (prime)

  • (prime)

  • (prime)

(The numbers 12, 14, 16, 18 are even, 15 is divisible by 3 and 5).

Step 3: Sum the prime numbers:

So the sum of the prime numbers between 10 and 20 is .

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