Math Riddles for High School Students Ready to Strategize

My tens digit is twice my ones digit. My hundreds digit is the tens digit minus three. What number am I?

Add me to myself, multiply by four, divide by eight, and I return. What number am I?

The sum of two numbers is 26 and their difference is 6. What are they?

If five cats catch five mice in five minutes, how many cats catch 50 mice in 50 minutes?

I become 20 when tripled and decreased by 4. What number am I?

How many times in 24 hours does a digital clock show matching hour and minute digits like 11:11?

What integer satisfies three times it plus five equals twice it plus 17?

I am a palindrome divisible by 3 and 11, between 400 and 500. What am I?

A faster train leaves 30 minutes after a slower train. Speeds are 60 and 45 mph. When does it catch up?

How many diagonals does a regular 12-sided polygon have?

A triangle has angles in the ratio 2 to 3 to 4. What are the measures?

The average of four numbers is 18. Three are 12, 20, and 26. What is the fourth?

I am a two-digit prime that becomes composite when reversed. What number am I?

The product of two consecutive positive integers is 132. What are they?

A sequence starts 2, 6, 12, 20. What is next?

What is the slope of a line through points (0, 3) and (4, 11)?

A right triangle has legs 6 and 8. What is the hypotenuse?

What is the next term: 3, 9, 27, 81?

If a circle has radius 6, what is its diameter?

What is the sum of the exterior angles of any polygon?

What value of x solves 2x - 7 = 15?

A quadratic has roots 4 and 8. What is their sum?

What is 2 to the fifth power?

What is the median of 4, 9, 13, 15, and 20?

If sin is not allowed, what triangle ratio compares opposite to adjacent?

What is the area of a rectangle with length 13 and width 7?

A code uses A=1. What does 13-1-20-8 spell?

What number is both a perfect square and a perfect cube between 1 and 100?

What is 15 percent of 300?

I am the written reason that proves the answer, not just the guess. What am I?