Multiple choice

The reminder of x divided by 9, 15 or 21 is 3. If x is an integer, what is the smallest possible value of x?

  1. 210

  2. 360

  3. 318

  4. 432
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

x = 9a + 3 = 15b + 3 = 21c + 3, a, b and c are all integers. So 9a = 15b = 21c, the least common multiple of 9, 15 and 21 will be 3*3*5*7 = 315. So 9a = 15b = 21c = 315, a = 35, b = 21, c = 15. Hence, x = 315 + 3 = 318.

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