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Difficulty: 3/102024 NMTC 2024 (Q33)

What is the least positive integer that is exactly divisible by all the integers from to ?

Options:

  • A.

    1260

  • 2520

  • C.

    5040

  • D.

    720

Guide / Hint

Hint 1: Understand that the number is the LCM of all numbers from 1 to 10.

Hint 2: Form the LCM by taking the highest power of each prime base appearing in the numbers 1 to 10: , , , and .

Hint 3: Multiply them: , and identify option index 1.

Solution

Step 1 (LCM Concept): The least positive integer divisible by all numbers from 1 to 10 is the Least Common Multiple (LCM) of the set .

Step 2 (Calculate the LCM): We factor each number and take the highest power of each prime:

  • Prime 2: highest power is (from 8)

  • Prime 3: highest power is (from 9)

  • Prime 5: highest power is (from 5, 10)

  • Prime 7: highest power is (from 7)

Step 3 (Conclusion): The least positive integer is 2520, which is at option index 1 in the options ['1260', '2520', '5040', '720'].

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    2024 NMTC 2024 Q33 - Olympiad Math Olympiad Question | Leminno