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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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31 problemsClear all filters

KA-0056
4 points, difficulty 2 of 3Level 3–4not yet calibrated
The two digits of a number are swapped and the number gets bigger by 36. Which of these could be the number?
NUM-01Place value and digit positionsalso NUM-02
KA-0057
3 points, difficulty 1 of 3Level 3–4not yet calibrated
What is 1 + 2 + 3 + ... + 20?
NUM-08Clever regrouping (pair to round numbers)also CNT-01
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-0061
3 points, difficulty 1 of 3Level 3–4not yet calibrated
Each shape stands for a whole number. A triangle plus a triangle plus a triangle is 12, and a triangle plus a square is 9. What is the square?
NUM-14Operation puzzles and cryptarithmsalso 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-0063
4 points, difficulty 2 of 3Level 3–4not yet calibrated
Which of these numbers can be divided exactly by both 4 and 9?
NUM-04Divisibility rules: 2, 3, 4, 5, 9, 10also NUM-01
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
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

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