Math Riddles for Kids

Imagine counting every person’s thumbs. Then multiply all those numbers together. The answer is not what you might expect. Think about exceptions.

Hint: Some people have zero thumbs.

A book lies open. The left and right page numbers add to 21. Multiply these numbers. What do you get?

Hint: The pages are consecutive numbers.

What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/10 of 1,000?

Hint: What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/1…

I have six zeros to play with. I know a secret: zero factorial equals one. Combine them with plus signs and a final factorial. What number appears?

Hint: Use factorials cleverly.

Take eight copies of the digit 8. Use only plus signs to connect them. Can you reach a big round number? Which one is it?

Hint: Arrange them by place value.

• I am a single digit.
• I am greater than two and less than nine.
• Count the sides of a hexagon, then add one.
• That sum reveals me.
• What number am I?

Hint: How many sides on a hexagon? Add 1.

What’s the least number of chairs you would you need around a table to sit four fathers, two grandfathers, and four sons?

Hint: What’s the least number of chairs you would you need around a table to sit four …

• Start with the number thirty.
• Divide it by a special fraction: one-half.
• Then add five to that result.
• The answer is bigger than you might think.
• Try it out!

Hint: Dividing by ½ is the same as multiplying by 2.

• You have two digits: six and seven.
• Place a tiny symbol between them.
• Now the number is more than six.
• But still less than seven.
• What did you use?

Hint: Think of how to write numbers like six and a half.

• I have three digits.
• My first digit is three less than the second.
• The second digit is four times the third.
• There may be more than one answer.
• Solve to find me!

Hint: Start by guessing the third digit.

Two islands sit in the Bering Strait. One is Russian, one is American. At 23:00 on the Russian isle, what does the clock show on the American isle?

Hint: Think about the International Date Line.

It’s almost midnight; the clock shows 11. You wait six hours. The hands spin past twelve. Where do they stop?

Hint: Clocks only go up to 12.

What year comes next in this sequence: 1973 1979 1987 1993 1997 1999

When can you add two to eleven and get one as the correct answer?

Start a timer at dawn. Add six hours to seven. You land on a number that seems wrong, until you check your watch.

Hint: Think about the face of a clock.

Train A leaves at 15:00, going 240 km/h. Train B leaves at 16:00, going 360 km/h. Both travel the same track. What time does B meet A?

Hint: Find how far ahead the first train is.

Uncle is 42, cousin is 6. Someday Uncle’s age will be exactly four times cousin’s. How many years must pass?

Hint: Make an algebra sentence.

Most polygons have many sides. But imagine a shape with only two straight lines. It’s impossible on flat paper, yet exists on a curved surface.

Hint: Think round, like a ball.

Which clock works best, the one that loses a minute a day, or the one that doesn’t work at all?

Hint: Which clock works best…

Which is heavier ? A pound of feathers or a pound of gold.