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Mystery Number

Brain Teaser: Can You Find the Mystery Number?

Allie Johnson

What do Nancy Drew, Sherlock Holmes and Miss Marple have in common? These famous fictional detectives all have an uncanny ability to crack tough cases. Even if you don’t stumble across mysteries in your daily life like these gumshoes do, seeking out a brain teaser, puzzle or riddle now and then offers a fun way to keep your mind sharp.

You’ll hone some of the same mental skills detectives use to do their work. These abilities include analytical skills, an eye for detail, resourcefulness and tenacity. Keeping these attributes sharp also can pay off by helping you solve challenges you face every day — from planning a vacation to making a medical decision.

Mysteries are a type of logic puzzle in which you get hints you must use to figure out a solution. Logic puzzles come in many forms, from word stories to math problems. But all logic games can help you improve these cognitive skills:

  • Critical thinking
  • Problem-solving
  • Reasoning

Some research shows that games, puzzles and other “informal mentally stimulating activities” may even lower the risk of cognitive impairment and dementia, according to the National Institute on Aging. How do these activities help the brain? They may create “cognitive reserves” that can assist the brain in adapting to changes caused by aging or health issues.

More research is needed, but some studies show that adults 65 and up who participated in brain training that involved their memory, reasoning and processing speed all had mental gains that lasted for two years.

So try your hand at “Can You Find the Mystery Number?” — a math and logic puzzle that will let you dust off your detective skills and study clues to come up with a solution. You’ll have to analyze the relationship of the numbers in the first two triangles to solve the mystery of the missing number in the third triangle. If you get stuck, scroll down for a hint or scroll to the bottom for the answer.

What's Your Number

Are you stuck? Here’s a hint: Addition, multiplication and division are all required to find the answer. Still stuck? Scroll to the bottom for the answer.

Answer To What's Your Number

How’d you do? Did you find this brain teaser easy or challenging? Let us know in the comments and try our other brain teasers.

13 Responses to "Brain Teaser: Can You Find the Mystery Number?"
    • Gail Miller | November 17, 2021 at 2:51 pm

      I can’t see the numbers too small

    • marita | October 23, 2021 at 6:55 pm

      I would love it

    • Joseph Gluzinski | October 23, 2021 at 4:41 pm

      Happiness abounds; it’s just waiting for you to give. Every person comes into this world with a pocket filled with happiness which is intended to be given away to everyone we meet in life. The pocket can never be emptied because it automatically refills as you reach in to share.
      What is in the pocket? It is LOVE, CONCERN, CARING, SHARING, SINCERE COMPLIMENTS, UNDERSTANDING FORGIVENESS ETC.

      YOU CAN DAILY TO ALL THAT YOU MEET AND THE POCKET WILL ALWAYS BE FULL.
      TRY TO BE THE FIRST PERSON TO EMPTY THE POCKET AND I GUARANTEE THAT YOUR LIFE WILL BE FFILLED WITH THAT SAME HAPPINESS. GOD BLESS

      Please share if you like it. Joseph Gluzinski

      • Sarah Buchanan | October 25, 2021 at 7:57 pm

        Joseph I love it. My goal in life have been emptying my pockets on a daily basis to the best of my ability and know how, with the help of the Creator. Doing so keeps you in a happy place and keep your mind occupied on the good things in life. What goes around comes back around in an abundance. Emptying your pockets with the content you speak of will change your life for the better and forever more. Continue to be blessed and to be a blessing to others.

    • Gina St Clair | October 23, 2021 at 12:54 pm

      Hard, but I got it. I used the hint which eliminated subtraction. Then I did the middle triangle by seeing 12/3=4 15/3=5 4+5=9 9*2=18. I used the same formula for the first triangle which creates decimals, but gave me the correct answer. Same with the third triangle, I changed the decimals to fractions (1/3 and 2/3) and got the right answer. Now I want to try more.

      • Extra Mile Staff | October 24, 2021 at 8:21 pm

        Gina – So glad you enjoyed it. You can check out more of our brain teasers here.

    • John Galaska | October 23, 2021 at 11:47 am

      @Eugene

      In the first one, if you add 7 to 8, multiply by 2, divide by the bottom 5, you get 6 in center.

      In the second one, add 12 to 15, multiply by 2, divide by bottom 3, you get 18.

      Following the pattern, you add 100 to 20, multiply by 2, divide by bottom 6 and get 40.

      I see it now but hadn’t initially, having possibly 216 as ? Fun stuff

    • Rich | October 23, 2021 at 9:39 am

      Very challenging puzzle. Even though you provided a hint, I was way off on the solution. Good one.
      Thank you

    • Eugene LeDuc | October 21, 2021 at 9:54 am

      The number in the center is 20. 100 + 20 = 120, 120/6 = 20
      Where did the 2 come from in your answer?

      • Sandra Sims | October 23, 2021 at 10:40 am

        Two times the top two numbers divided by the bottom number. 40

      • Mary Meehan | October 23, 2021 at 2:22 pm

        The 2 comes from the instructions. 20 x 2 = 40

      • Lyell | October 23, 2021 at 2:24 pm

        The other sums were multiplied by 2 to get the answer, so 2×20=40. It took me awhile, but I got it. Good to challenge the brain.

      • Anthony Tyas | October 23, 2021 at 5:04 pm

        The 2 came from the relationship of the first 2 figures

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