KA-0049●●●5 points, difficulty 3 of 35 ptLevel 5–6not yet calibratedThe 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-0050●○○3 points, difficulty 1 of 33 ptLevel 3–4not yet calibratedToma spent 4 euros, then spent half of what was left, and now has 6 euros. How much did she start with?LOG-08Working backwardsalso MOD-06
KA-0051●○○3 points, difficulty 1 of 33 ptLevel 3–4not yet calibratedHow many of the numbers from 1 to 20 are not multiples of 3?CNT-09Complementary countingalso CNT-01
KA-0052●●●5 points, difficulty 3 of 35 ptLevel 5–6has a figurenot yet calibratedA 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 34 ptLevel 5–6not yet calibratedWhat is the remainder when 2 to the power 30 is divided by 7?NUM-06Remainders and modular cyclesalso PAT-03, NUM-07
KA-0054●○○3 points, difficulty 1 of 33 ptLevel 3–4has a figurenot yet calibratedA rectangle is divided by two vertical lines into three parts. How many rectangles of any size are in the picture?CNT-13Counting shapes hidden inside a figurealso CNT-01
KA-0055●○○3 points, difficulty 1 of 33 ptLevel 3–4not yet calibratedIn the number 4073, what is the value of the digit 7?NUM-01Place value and digit positions
KA-0056●●○4 points, difficulty 2 of 34 ptLevel 3–4not yet calibratedThe 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 33 ptLevel 3–4not yet calibratedWhat is 1 + 2 + 3 + ... + 20?NUM-08Clever regrouping (pair to round numbers)also CNT-01
KA-0058●●○4 points, difficulty 2 of 34 ptLevel 5–6not yet calibratedWhat is 2 + 4 + 6 + ... + 100?NUM-08Clever regrouping (pair to round numbers)also PAT-02
KA-0059●○○3 points, difficulty 1 of 33 ptLevel 5–6not yet calibratedA 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 35 ptLevel 5–6not yet calibratedA 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