What better way to encourage thinking outside the box than with math brain teasers? They usually focus more on using logic than on being a math whiz, so everyone needs to think creatively. Here are some popular math brain teasers for students of all ages. Perfect for ringing a bell, adding extra credit, or filling in the last few minutes at the end of class.
Plus, by clicking the button below, you’ll receive a Google Slideshow of all the math brain teasers compiled in an easy-to-present format.
50 math brain teasers
1. Using only addition, add eight eights to find the number 1,000.
Answer: 888 + 88 + 8 + 8 + 8 = 1,000.
2. Two years ago, I was three times my brother’s age. In three years, I will be twice as old as my brother. How old are we now?
Answer: My older brother is 17 years old and my younger brother is 7 years old.
3. If half a chicken lays one and a half eggs in one and a half days, how many eggs will six chickens lay in six days?
Answer: 2 dozen, or 24 eggs.
4. When is 9 + 5 = 2?
Answer: When telling the time. 9:00 + 5 hours = 2:00.
5. A farmer had 17 sheep. All but nine escaped. How many sheep does she have left?
Answer: 9.
6. The boy is 2 years old. His older brother is half his age. When the first boy turns 100 years old, how old will his younger brother be?
Answer: 99.
7. Create a real math equation using the numbers 2, 3, 4, 5 and the symbols + and =.
Answer: 2 + 5 = 3 + 4.
8. If 3 cats can catch 3 rabbits in 3 minutes, how long does it take for 100 cats to catch 100 rabbits?
Answer: 3 minutes.
9. Mr. Lee has four daughters. His daughters each have one sibling. How many children does Mr. Lee have?
Answer: 5 (The daughters all have the same siblings.)
10. What single digit occurs most frequently between 1 and 1,000?
Answer: 1.
11. Which is heavier: 16 ounces of feathers or 1 pound of pure gold?
Answer: The weight is the same. No matter what ingredients you measure, 16 ounces = 1 pound.
12. Jake bought a pair of shoes and a shirt. Total cost was $150. The shoes cost $100 more than the shirt. How much did each item cost?
Answer: Shoes cost $125 and shirts cost $25.
13. You have two coins totaling 30 cents. One of them is not a nickel. What are two coins?
Answer: 1/4 and 1 nickel. (Only one coin is not a nickel!)
14. A + B + C = D, and A x B x C = D. What are the numbers for these two equations?
Answer: A = 1, B = 2, C = 3, D = 6.
15. Work this out in your head (don’t write it down). Add 40 to 1,000. Add another 1,000. Now add 30. Add another 1,000. Now add 20. Add another 1,000. Now add 10. How much is the total?
Answer: 4,100.
16. A grandmother died and left half of her estate to her granddaughter and the other half to her grandson. She left one-sixth to her brother and the remaining $1,000 to the animal shelter. How much did she leave in total?
Answer: $12,000.
17. There are 18 white socks and 18 blue socks in the sock drawer. What is the minimum number of socks you need to remove to ensure a matching match without examining them?
Answer: 3.
18. You planted sunflower seeds in the garden. The number of flowers doubles every day. If it takes 52 days for the flowers to fill the garden, how many days does it take for the flowers to fill half the garden?
Answer: 51.
19. There are 100 houses in the neighborhood where Alex and Dev live. Alex’s house number is the reverse of Dev’s house number. The difference in their house numbers ends in 2. What is their house number?
Answer: 19 and 91.
20. What can you put between 8 and 9 to make the result greater than 8 and less than 9?
Answer: Decimal (8.9 is greater than 8 and less than 9).
21. If you multiply this number by any other number, you will get the same answer every time. What is the number?
Answer: Zero.
22. If there are 6 oranges in the basket and you take out 4, how many oranges are there?
Answer: 4 (You took 4 oranges, so there are 4 oranges!)
23. There are 8 apples in the basket. Eight people each receive an apple, but there is still one apple in the basket. How can this happen?
Answer: The eighth person took the basket with one apple still in it.
24. Multiply all the numbers on your phone’s numeric keypad. How much is the total?
Answer: Zero (the phone number pad contains digits 0-9).
25. The Garcia family has seven children, each born two years apart. If Garcia’s eldest son is 19 years old, how old is Garcia’s youngest son?
Answer: 7.
26. Two mothers and two daughters ate one egg each for breakfast, but only three together. How can this happen?
Answer: It was just the grandmother, daughter, and granddaughter.
27. A 300-foot train traveling at 300 feet per minute must pass through a 300-foot-long tunnel. How long does it take for a train to pass through the tunnel?
Answer: 2 minutes. (The first part of the train takes one minute, and the rest of the train takes another minute to go through the tunnel.)
28. I’m a 3-digit number. My second digit is four times as large as my third digit. My first digit is 3 fewer than my second digit. What number am I?
Answer: 141.
29. Tom was asked to draw numbers on the outside of 100 apartments. This means you have to draw numbers from 1 to 100. How many times must you draw the number 8?
Answer: 20 times (8, 18, 28, 38, 48, 58, 68, 78, 80, 81, 82, 83, 84, 85, 86, 87, 88) [two 8s]89, 98).
30. Ellie works at an aquarium. When she tries to put each turtle in its own tank, there is one turtle too many. But if you put two turtles in one tank, one tank is too many. How many turtles and aquariums does Ellie have?
Answer: Ellie has three aquariums and four turtles.
31. If eggs cost 12 cents, how many eggs can you get for one dollar?
Answer: 100 eggs (each egg costs 1 penny)
32. If you toss a coin 100 times and it comes up heads each time, what is the probability that it will come up heads on the next toss?
Answer: 50/50 (There is no difference in the previous toss; the probability of heads or tails is always the same.)
33. You are visiting a clothing store whose products are priced in a strange way. Vests are $20, socks are $25, ties are $15, and blouses are $30. I want to buy underwear. How much does it cost?
Answer: $45. The cost of the item is $5 for each letter used to spell the word.
34. How can I make this equation, 81 x 9 = 801, correct?
Answer: Flip: 108 = 6 x 18.
35. You’re going to use your birthday money to take your friends to the movies. Is it cheaper to take one friend to the movies twice or to take two friends to the movies at the same time?
Answer: Since you are bringing two friends at the same time, you can only buy three tickets in total. If you want to bring one friend twice, you need to buy one ticket each time, for a total of 4 tickets.
36. A snail climbs a wall 3 feet every day, but every night it slides down 2 feet while it sleeps. If the wall is 30 feet high, how many days will it take for the snail to reach the top?
Answer: 28 days. The snail grows 1 foot each day, reaching 27 feet on the 27th day. On the 28th day, climb the final 3 feet to reach the summit.
37. Divide 40 in half and add 10. What will be the result?
Answer: 90. The instructions say to divide it in half, not to cut it in half. So the equation is 40 ÷ .5 = 80 + 10 = 90.
38. Add me to myself and multiply by 4. Divide me by eight and you’ll have me again. What number am I?
Answer: This works with any number.
39. Lynn is four times the age of her daughter Rosa. In 20 years, Lin will be twice her daughter’s age. How old are Lin and Rosa now?
Answer: Lynn is 40 years old and Rosa is 10 years old.
40. A box contains 13 blue marbles, 13 red marbles, and 13 green marbles. If you can’t see inside the box, what is the minimum number of marbles you need to take out to ensure you get one of every color?
Answer: 27. You may need to remove all marbles of two colors (26) before drawing the third color (+1).
41. A store offers bats and balls for a total of $1.10. The bat costs one dollar more than the ball. What is the individual price of each item?
Answer: The ball costs 5 cents and the bat costs $1.05.
42. Find two numbers whose sum of squares is 100 (neither number is zero).
Answer: 8 and 6 (64 + 36 = 100).
43. Miguel, Sara, and Olive share a box containing 120 M&Ms. Miguel eats half of the candy, Sara eats a third, and Olive eats a tenth. How many M&Ms are left?
Answer: 8. Miguel eats 60 pieces, Sara eats 40 pieces, and Olive eats 12 pieces. This leaves 8 candies left uneaten.
44. What is unique about this number 8,549,176,320?
Answer: When spelled as a word, it contains the numbers 0 through 10 in alphabetical order. (8, 5, 4, etc.)
45. Arrange the numbers 1 through 9 in a 3 x 3 grid so that each row, column, and diagonal have the same sum.
Answer: 1st row: 8 3 4, 2nd row: 1 5 9, 3rd row: 6 7 2.
46. The circumference of a rectangle is 24 inches. What are the dimensions of the rectangle if its length is twice its width?
Answer: Width = 4 inches, length = 8 inches.
47. I am a 4-digit number (ABCD). When you multiply by 4, the answer is the same 4-digit number reversed (DCBA). What number am I?
Answer: 2,178.
48. What is the next number in this series? 7,645 5,764 4,576 ____.
Answer: 6,457 (moves the last digit to the beginning each time)
49. A triangle has three angles, all of which are square numbers. What are the angles of this triangle?
Answer: 16 degrees, 64 degrees, 100 degrees.
50. What is the smallest integer that uses every vowel exactly once when written out in words?
Answer: 5,000
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