Algebra and Number Sense
My tens digit is twice my ones digit. My hundreds digit is the tens digit minus three. What number am I?
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462.
Add me to myself, multiply by four, divide by eight, and I return. What number am I?
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Any number.
The sum of two numbers is 26 and their difference is 6. What are they?
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16 and 10.
If five cats catch five mice in five minutes, how many cats catch 50 mice in 50 minutes?
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Five cats.
I become 20 when tripled and decreased by 4. What number am I?
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8.
On a 24-hour digital clock, how many times in a day do the hour and the minute show the same two-digit number, like 11:11 or 05:05?
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24 times (00:00, 01:01, … 23:23).
What integer satisfies three times it plus five equals twice it plus 17?
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12.
I am a three-digit palindrome between 400 and 500. My digits add up to 16. What am I?
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484.
A faster train leaves 30 minutes after a slower train. Speeds are 60 and 45 mph. When does it catch up?
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One and a half hours after the faster train leaves.
How many diagonals does a regular 12-sided polygon have?
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54 diagonals.
Geometry and Sequences
A triangle has angles in the ratio 2 to 3 to 4. What are the measures?
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40, 60, and 80 degrees.
The average of four numbers is 18. Three are 12, 20, and 26. What is the fourth?
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14.
I am a two-digit prime that becomes composite when reversed. What number am I?
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23.
The product of two consecutive positive integers is 132. What are they?
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11 and 12.
A sequence starts 2, 6, 12, 20. What is next?
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30.
What is the slope of a line through points (0, 3) and (4, 11)?
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2.
A right triangle has legs 6 and 8. What is the hypotenuse?
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10.
What is the next term: 3, 9, 27, 81?
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243.
If a circle has radius 6, what is its diameter?
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12 units.
What is the sum of the exterior angles of any polygon?
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360 degrees.
Math Club Challenge Extras
What value of x solves 2x - 7 = 15?
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11.
A quadratic has roots 4 and 8. What is their sum?
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12 roots total.
What is 2 to the fifth power?
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32.
What is the median of 4, 9, 13, 15, and 20?
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13.
If sin is not allowed, what triangle ratio compares opposite to adjacent?
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Tangent.
What is the area of a rectangle with length 13 and width 7?
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91.
A code uses A=1. What does 13-1-20-8 spell?
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Math.
What number is both a perfect square and a perfect cube between 1 and 100?
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64.
What is 15 percent of 300?
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45.
I am the written reason that proves the answer, not just the guess. What am I?
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A mathematical justification.
FAQ
Are answers included?
Yes. Every riddle includes the answer.
Best classroom use?
Use them for math club, bell work, SAT prep, or enrichment.
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