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177 problems, every one written from scratch, every wrong answer carrying the mistake that produces it. 708 explanations in all.

Level

1–2
3–4
5–6
7–8
9–10
11–12

Point value

3 pt
4 pt
5 pt

Strand

NUMNumber & Arithmetic
CNTCounting
GEOGeometry & Visualization
LOGLogic & Deduction
PATPatterns & Sequences
MODModeling & Word Problems
CFTContest Craft

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5 problemsClear all filters

KA-0037
5 points, difficulty 3 of 3Level 5–6not yet calibrated
What is the units digit of 7 multiplied by itself 2026 times, that is 7 to the power 2026?
NUM-07Last-digit behavior of products and powersalso NUM-06, PAT-03
KA-0049
5 points, difficulty 3 of 3Level 5–6not yet calibrated
The numbers 1 to 9 are placed in a row in some order. Can every neighbouring pair add up to an odd number?
NUM-03Parity of numbers (odd/even behavior)also LOG-05, CNT-04
KA-0060
5 points, difficulty 3 of 3Level 5–6not yet calibrated
A and B are different digits. The two-digit number AB added to the two-digit number BA gives 132. What is A + B?
NUM-14Operation puzzles and cryptarithmsalso NUM-01, LOG-08
KA-0135
5 points, difficulty 3 of 3Level 3–4not yet calibrated
How many two-digit numbers have both of their digits odd?
NUM-02Digit-constraint puzzlesalso NUM-03, CNT-03
KA-0158
5 points, difficulty 3 of 3Level 7–8not yet calibrated
What is the last digit of 3 multiplied by itself 2026 times, that is, of 3 to the power 2026?
NUM-07Last-digit behavior of products and powersalso NUM-06, PAT-03