Skip to main content
PPrime
← Back to archive

Problem #71 · October 6, 2026

Divisibility rules

Which of the following numbers is divisible by 99?
  1. A234
  2. B428
  3. C512
  4. D623
  5. E715

WORKED EXAMPLE

Solution

For a number to be divisible by 99, the sum of its digits must be divisible by 99. Because 2+3+4=92+3+4=9, the number 234234 is divisible by 99. The digit sums of the remaining numbers, (1414, 88, 1111, 1313), are not divisible by 99.
Solve today's problem