Puzzling Numbers Games

Mathematics play a big role in science and research! But don't let that scare you! Math can be fun, and very illuminating! Sometimes it works just like magic! You don't believe that? Then try the following games and be prepared to be surprised.

Phone a Friend?
Wisdom of the Ages
Be a Math Wizard (or Mind Reader?)
Trouble in Denmark
Pick-Pocket Game
Puzzling Odds
Why is that so?

Phone A Friend

It's time to phone a friend for a little math fun...get your calculator...this works!
  1. What are the first 3 digits of your phone number? (ignore your area code and use only your seven digit phone number)
  2. Multiply by 80
  3. Add 1
  4. Multiply by 250
  5. Add in the last four digits of phone number
  6. Add in the last four digits of phone number again
  7. Subtract 250
  8. Divide by 2...
Is the answer your phone number? Weird, eh? Explanation.

Wisdom of the Ages

Follow the instructions carefully, ONE LINE AT A TIME. Be sure to do exactly what it says before moving to the next instruction.

  1. Write down the number of the month you were born
  2. Multiply it by 4
  3. Add 13
  4. Multiply the result by 25
  5. Subtract 200
  6. Add the day of the month on which you were born
  7. Multiply by 2
  8. Subtract 40
  9. Multiply the result by 50
  10. Add the last two digits of the year of your birth
  11. Finally, subtract 10,500
Notice anything funny about your answer?

The result should be your birth month, day, and last two digits of the year.

Be a Math Wizard (or Mind Reader?)

Here is a math trick you can play on your friends to show them what a math whiz you are! Tell a friend that the two of you will pick five 5-digit numbers at random, and then will add them together -- but, amazingly, after just hearing the first number and before the others have even been selected, you'll be able to accurately predict what the TOTAL of those five numbers will be!

Steps:

  1. Have a friend write down a 5-digit number -- for example, he might write down 67,812.
  2. Then on a separate piece of paper, you can immediately write down the final "answer" to this quiz (the total of all five numbers), even though four of the numbers haven't even been selected yet! For the example given, 67,812, the answer will be 267,810.
  3. Announce that you have "predicted" the final answer and written it down as proof -- but don't show it yet. Just fold the piece of paper over to keep that answer hidden till the end of the "trick".
  4. Then have your friend write down a second 5-digit number right beneath the first one.
  5. You then quickly write down a third 5-digit number right below it (but you'll have to know what to write -- to find out, visit the instructions below!).
  6. Then have your friend write a fourth 5-digit number under your number. Then you immediately write a fifth 5-digit number beneath it (again, you'd select that number according to the instructions below ).
  7. Then ask your friend to add up the five 5-digit numbers that have been written down.
  8. Compare that answer to the one you wrote down after the first number was selected.
Amazingly, they will be identical! But how could you do that? How could you predict the total after just hearing the first number? Just follow the instructions below!

Instructions/Answer

Here is the trick:
Take the first number and subtract 2 from it then put the number "2" in front of it. (For example, if the number was 67,812, it would be 267,810). That will be the final answer. Then, when you see the second number your friend writes down you mentally subtract each digit of that number from 9, and write that answer for the third number. (For example, if your friend's second number is 11,111, then the number you would choose and write down would be 88,888. Or, if your friend's number is 56,123, then your next number would be 43,876. The key here is that each of your friend's number's digits, when added to the corresponding digit of your number, must total 9.) Then you ask your friend to write down a fourth number, and again you subtract each digit of that number from 9 (do this silently!), and write that answer down as the fifth number. For example, if the second number is 12,345, then you would write 87,654 as the third number because(12345 + 87654=99999). When the 5 numbers the two of you selected are all added together, the total will be identical to the number you originally wrote down and set aside! It works every time. Try it and see!

Trouble in Denmark Game

Follow the instructions carefully, ONE LINE AT A TIME. Be sure to do exactly what it says before moving to the next instruction.

  1. Pick a number from 5 to 9
  2. Subtract 5
  3. Multiply by 3
  4. Square the number (multiply it by itself)
  5. Add the digits in the number together until you get only one digit; i.e. 64: 6 + 4 = 10; 1 + 0= 1
  6. If the number is less than 5, add five. Otherwise subtract 4.
  7. Multiply it by 2
  9. Subtract 6
  10. Give the digit its corresponding letter in the alphabet (for example: 1=A, 2=B, 3=C, 4=D...26=Z, etc)
  11. Pick a name of a country (NOT A STATE) that begins with that letter.
  12. Take the second letter in the country name and think of a mammal that begins with that letter.
  13. Think of the most common color of that mammal.

DO NOT LOOK AT THE ANSWER UNTIL YOU HAVE COMPLETED ALL OF THE ABOVE STEPS IN ORDER!

ANSWER: A GRAY ELEPHANT FROM DENMARK!

If you did not get that exact answer,you either thought of a really unique country, a really unique mammal, or you need to re-check your math and try again!

Some of the other creative answers we've received from our readers are: a black and white Echidna from Denmark (the Echidna is native to New Guinea and Australia); a brown elk From Denmark; and a brown joey (baby kangaroo) in Djibouti (Djibouti is a country created from the French Territory of the Afars and Issas, French Somaliland).

Pick-Pocket Game

This may take a calculator, but it will be worth it! You can impress your friends and family by correctly guessing the amount of change they have in their pockets!

Notice that the first two digits will be the person's age, and the last two digits are the amount of the person's pocket change.

Surprising Odds!

You can probably just do this math in your head. Answer as QUICKLY as possible, but don't advance until you've done each of them.

WHAT IS:

You probably picked: 7 (seven). Most people do for some reason.

Why is that so?

Here's an odd little puzzle one of our statisticians brought to light from his high school days. For some unknown reason, odds are that if you answer quickly you will come up with the same answer as the majority of other people. But we have no idea why that is so. Remember to answer EVERY question as QUICKLY as possible! You can probably just do this in your head. Are you ready?

Quick, what is the first vegetable to come to your mind?
Answer quickly; if you take too long before answering, it won't work!

We bet that you picked carrots! Most people do for some reason. Explanation of Phone Math Teaser This is a little algebra problem. Let X denote the first three digits of the phone number and Y the last four digits. Then let's take the calculations a step at a time.
  1. X
  2. 80X
  3. 80X + 1
  4. 250 (80X+1) or 20,000X + 250
  5. 20,000X + 250 + Y
  6. 20,000X + 250 + 2Y
  7. 20,000X + 250 + 2Y -250 or 20,000X + 2Y
  8. (20,000X + 2Y)/2 or 10,000X + Y
Thus, no matter what your phone number is, the final number will repeat your phone number. The 10,000 multiplier is needed to move the first three digits over four decimal places). [ Brainteaser Index ]
[ NIEHS Kids' Pages Index ]

Privacy and Accessibility,
Disclaimers and Copy Requests
NIEHS Kids' Pages Home
NIEHS Home

Links Disclaimer and Caution

When you encounter the alt tag or words "Non-NIEHS Link", it means that by following that link you will be leaving the NIEHS website. NIEHS is NOT responsible for non-NIEHS websites. Sites maintained by outside organizations may be changed without notice to NIEHS. Therefore, unless the link is to another U.S. government sponsored webpage, endorsement by NIEHS is not implied, and NIEHS does not guarantee their continuing safe content or privacy policies. So please ask your parent or guardian before continuing to any non-NIEHS website, and especially before providing any information via the internet or by e-mail. When last reviewed, the websites linked from the NIEHS Kids' Pages seemed suitable for you to visit, but that may have changed; if you have any difficulties or concerns with any linked materials, please let us know.

NIEHS Kids' Pages are supported by the NIEHS Office of Communications and Public Liaison,
PO Box 12233, NH-10, Research Triangle Park, North Carolina 27709. Telephone: (919) 541-3345.
This page was last modified and reviewed for accessibility by the NIEHS Office of Management on .
Department of Health and Human Services (DHHS), National Institutes of Health (NIH), National Institute of Environmental Health Sciences (NIEHS).
Office of Inspector General, DHHS

DHHS logo NIH logo NIEHS logo USA.Gov logo