How does 111 equal 13

The next time you are with a group of people, and you want to impress them with your psychic powers, try this. Number everyone in the group from 1 to however many there are.

Get a piece of string, and tell them to tie it on someone's finger while you leave the room or turn your back. Then say you can tell them not only who has it, but which hand and which finger it is on, if they will just do some easy math for you and tell you the answers. Then ask one of them to answer the following questions:. Ask them to tell you the answer. Then mentally subtract The remainder gives the answer, beginning with the right-hand digit of the answer.

The right-hand digit 3 tells you the string is on the third finger. The left-hand digit tells you it is Player 6 who has the string. Published by Sterling Publishing Co. Stay tuned for more Math Tricks.

They will be added from time to time, so be sure to check in again. Math Tricks for All Ages This web page is devoted to the incredibly boffo idea that math can be fun! If you're using Netscape, Do Not Scroll down the page while this loads. Explore Geometry in a fun and interactive way. Try it, you'll like it. But remember we were first. Magic Addition Trick 1 Amaze the peons with this one.

It's simple. It's effective. It gets them every time. Ask your mark to pick three 3 different numbers between 1 and 9. Tell him or her or her or him to write the three numbers down next to each other, largest first and smallest last, to form a single 3-digit number. Next have her or him form a new 3-digit number by reversing the digits, putting the smallest first and the largest last.

And write this number right underneath the first number. Now have him or her subtract the lower and smaller 3-digit number from the upper and larger 3-digit number.

Tell them not to tell you what the result is. Now you have a choice of wrap-ups: Ask your friend to add up the three digits of the number that results from subtracting the smaller from the larger 3-digit number.

Then amaze him or her by teling them what the sum of those three numbers is. The sum of the three digit answer will always be 18! Tell your friend that if she or he will tell you what the first OR last digit of the answer is, you will tell her or him what the other two digits are. This is possible because the middle digit will always be 9, and the other two digits will always sum to 9!

So to get the digit other than the middle one which is 9 and other than the digit that your friend tells you, just subtract the digit your friend tells you from 9, and that is the unknown digit. Back to Top Magic Square 15 Every row and column sums to 15 in this magic square. So do both diagonals! Some necessary rules and definitions: Let the letters a , b , and c stand for integers that is, whole numbers. Always choose a so that it larger than the sum of b and c.

This guarantees no entries in the magic square is a negative number. This quarantees you won't get the same number in different cells. Using the formulas in the table below, you can make magic squares where the sum of the rows, columns, and diagonals are equal to 3 X whatever a is. Back to Top Upside Down Magic Square Here's a magic square that not only adds up to in all directions, but it does it even when it's upside down!

If you know the trick, you will never lose, and will probably will most times. The magic square look like this: 8 1 6 3 5 7 4 9 2 Because this is a magic square, every row and every column and every diagonal adds up to Just follow these easy steps: Shuffle the cards to mix them thoroughly.

Deal out 36 cards into a pile. Ask a friend to pick one of the 36 cards, look at it and memorize it, and then put it back in the pile without letting you see it. Shuffle the 36 cards. Lay the 36 cards out in 6 rows of 6 cards each.

Be sure to deal the top row from left to right. Then deal the second row beneath it from left to right. And so on with each succeeding row laid out underneath the one before. Ask your friend to look at the cards and tell you which row the chosen card is in.

Remember what number the row is. Carefully pick the cards up in the same order you laid them down. So the first card on the left of the top row is on top of the stack, and the last card on the right of the bottom row is on the bottom of the stack. Now lay the cards down in 6 rows of 6 cards each, but this time spread the card one column at a time.

Instead of proceeding from one row to the next, proceed from one column to the next. Lay the first six cards in a column from top to bottom on the far left. Then lay out the next six cards in a second column of six cards just to the right of the first column of six cards.

Continue doing this until you have 6 columns of 6 cards each which looks the same as 6 rows of 6 cards each -- because it is the same. Once again ask your friend which row contains the chosen card. When you friend tells you which row the card is in, you can say what the exact chosen card is. If your friend said the card was in row 2 the first time, and in row 5 the second time, then the chosen card is the one in the second column of the fifth row.

This is because the way you arrange the cards, what were rows the first time around become columns the second time around. Back to Top Lightning Calculator Here's a trick to wow them everytime! Back to Top Did You Know? One pound of iron contains an estimated 4,,,,,,,, atoms. The earth travels over one and a half million miles every day. There are 2,, rivets in the Eiffel Tower. Back to Top A Math Trick for This Year This one will supposedly only work in , but actually one change will let it work for any year.

Pick the number of days a week that you would like to go out Multiply this number by 2. Add 5. Multiply the new total by They took the last digit from the right as the first digit on the left. The remaining digit s on the right are the some of the digits on the right. So for the answer starts with 3 the last number and ends with 5 the sum of 1, 1, and 3. Again, this matches all the test cases. I was trying to solve a different problem. I assumed the numbers were actually equal.

Of course is not equal to 13 in our familiar decimal numeral system, but programmers are used to working with alternative bases like binary or base 2 , octal or base 8 and hexadecimal or base Note: Once you go past decimal, or base 10, the number system involves letters.

I find it interesting that three pretty simple patterns all work for 7 straight test cases, even though my interpretation solved a different problem!

However, they do begin diverging at The way the problem is stated is not precise. The popular solutions assume there is an implicit function.