To test divisibility or find remainders quickly, sum the digits (for 3 and 9) or alternate digit signs (for 11). To check large 3-digit multiplication A × B = C, multiply the remainders of A and B: they MUST equal the remainder of C! If remainders differ, the answer is guaranteed wrong in 5 seconds.
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Correct!
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Session Completed!
Skill: Divisibility (3, 9, 11) & Multiplication Sanity Check
100%
10 of 10 correct in 18.4s (avg 1.8s/q)
Question Breakdown & Solutions:
| # | Problem | Your Choice | Correct | Step-by-Step Reasoning |
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