Multiple Choice Question (MCQ)

What is the least positive integer that is divisible by both 2 and 5 and leaves a remainder of 2 when it is divided by 7?

  1. ×

    20

  2. 30

  3. ×

    50

  4. ×

    65

  5. ×

    75

Collected in the board: Number Theory

Steven Zheng posted 3 months ago


Answer

  1. If an integer is divisible by both 2 and 5, the number in its ones place must be 0. So D and E are excluded.

    Then apply the 2nd condition to check if the number leaves 2 when it is divided by 7.

    30 \mod 7 =2

    Correct choice is B.


Steven Zheng posted 2 weeks ago

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