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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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84 problemsClear all filters

KA-0045
5 points, difficulty 3 of 3Level 5–6not yet calibrated
A number is 4 more than a third of itself. Which of the choices is that number?
CFT-04Back-solve from the answer choicesalso CFT-05, MOD-01
KA-0047
5 points, difficulty 3 of 3Level 5–6not yet calibrated
On a 4 by 4 board, how many aligned squares of any size are there, counting 1 by 1, 2 by 2, 3 by 3 and 4 by 4?
CNT-12Counting by position (sliding window)also CNT-04, GEO-02
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-0052
5 points, difficulty 3 of 3Level 5–6has a figurenot yet calibrated
A circle of radius 5 is drawn inside a square of side 10, touching all four sides. What fraction of the square is outside the circle, to the nearest tenth?
GEO-04Area by subtraction (shaded regions)also GEO-03, GEO-07
KA-0053
4 points, difficulty 2 of 3Level 5–6not yet calibrated
What is the remainder when 2 to the power 30 is divided by 7?
NUM-06Remainders and modular cyclesalso PAT-03, NUM-07
KA-0058
4 points, difficulty 2 of 3Level 5–6not yet calibrated
What is 2 + 4 + 6 + ... + 100?
NUM-08Clever regrouping (pair to round numbers)also PAT-02
KA-0059
3 points, difficulty 1 of 3Level 5–6not yet calibrated
A tap drips about 3 times a minute. Roughly how many drips is that in one day?
NUM-12Estimation and order of magnitudealso MOD-07
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-0062
4 points, difficulty 2 of 3Level 5–6not yet calibrated
24 pencils and 36 erasers are shared into identical gift bags, using every item. What is the largest number of bags possible?
NUM-05Factors, multiples, LCM and GCD by listingalso NUM-04
KA-0064
3 points, difficulty 1 of 3Level 5–6not yet calibrated
Three quarters of a class of 28 travelled by bus. How many did not travel by bus?
NUM-09Fractions of a quantityalso CNT-09
KA-0065
4 points, difficulty 2 of 3Level 5–6not yet calibrated
A price goes up by 20%, then down by 20%. Compared with the original price, the final price is:
NUM-10Percentages and simple discountsalso NUM-09
KA-0066
4 points, difficulty 2 of 3Level 5–6not yet calibrated
The mean of four numbers is 9. Three of them are 5, 8 and 12. What is the fourth?
NUM-15Means, and working backwards from a meanalso LOG-08

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