What are some of the coolest calculator tricks?

Method 1 of 3:Doing the “Number 7” Trick 1. Tell someone to secretly select a 3-digit number and enter it twice into a calculator.

Make sure they do not show you the calculator’s display. Stand across the room from the person and make it seem like you are trying to read their mind.

For example, they could enter "123123."

2. Announce that the number is divisible by 11 and have them check it.

Dramatically announce this from across the room. Have them verify it and then tell the audience that you are right.

For instance, if they entered 123123, then they would divide it by 11 and get 11,193.

3. Tell them to divide that result by 13.

Announce from across the room that the result is divisible by 13. Tell them to do it on the calculator to prove it.

For example, if their last result was 11,193, then they would divide it by 13 and get 861.

4. Tell them to divide the result by the original 3-digit number.

Remember that they chose a 3-digit number and entered it twice. Make sure they only divide the result by 3-digits, rather than the 6 they entered at the beginning.

For instance, if their last result was 861, and the original number was 123, they would divide 861 by 123 to get the number 7.

5. Announce that the final answer is 7.

Tell them without looking at the screen. Have them show the audience, if you have one, to prove that you are right.

You can switch this trick up by having them divide the result by 7 in step 3, and announce that the result is 13 in the final step.

Method 2 of 3:Performing the “Secret of 73” Magic Trick 1. Write "73" on a piece of paper, fold it, and give it to a friend or volunteer.

Don't let anyone see the number your write down. You'll reveal this secret number at the end of the trick, to your audience's delight.

2. Tell your volunteer to pick a 4-digit number and put it into the calculator twice.

Any 4-digit number will work for this trick. Hand the calculator to the volunteer and have them enter the number.

For instance, if your volunteer picks the number "7893," they would type "78937893" into the calculator.

3. Announce that the number is evenly divisible by 137.

Have your volunteer verify this by dividing the 8-digit number in the calculator by 137. Any number made by repeating a 4-digit number twice will be evenly divisible by 137.

For example, 78,937,893 divided by 137 is 576,189.

4. Tell your volunteer to divide the answer by the original 4-digit number.

Your volunteer will get an answer of 73 every time if you've followed the directions right. It doesn’t matter which number they started with.

For instance, after dividing 78,937,893 by 137 to get 576,189, the volunteer would divide 576,189 by 7,893.

5. Command your volunteer to reveal your prediction.

Have your friend or volunteer open the folded piece of paper. Be prepared for your audience to go wild when your prediction of 73 is revealed!

Don't reveal the math behind the trick! A good magician knows how to keep their secrets.

Method 3 of 3:Reading Someone’s Mind 1. Tell someone to pick a number from 1-9 without telling you.

Explain to them that you are going to tell them what number they chose at the end. Put on an act that you are reading their mind while they are thinking of a number.

This is a super easy math trick that is easy to figure out at the end, but it’s still fun to put on a show!

2. Have them multiply their number on a calculator by "9," then by "12345679."

Notice that there is no "8" in the second sequence of numbers. Make sure they multiply the number they chose by "9", then by "12345679," with no "8" in order for the trick to work.

Keep pretending you are reading the person’s mind while they perform the multiplication.

3. Make them show you the results or pass you the calculator.

Tell them you will divide what number they chose at the beginning from the result on the calculator. Have them hold the calculator to face you so you can see the number or hand it to you so you can look.

If you have an audience, don’t let them see the result on the screen in order to create a more dramatic effect.

4. Look at the number to determine what their original number was and tell them.

Whatever number you see repeating on the screen is the number they chose at the beginning. There will only be a string of a single repeating number.

For example, if they chose "1," then the calculator will show "111111111."