Let's Troll Your Friends With These Cool Simple Math Tricks

Admit it, Math is like magic, but better! And you can wow your friends with the following Math tricks.

Tell someone’s age by shoe size

First, write down your shoe size in the whole number format (round it up if you have to), it must be in US size too.

Now multiply the shoe size by 5.

Next, add 50 to the result.

Multiply the answer by 20.

Now, if you are living in 2019, add 1019 to the result from above, if you are living in 2020, add 1020, etc.

Subtract your year of birth from the answer.

Your age is shown in the last 2 digits with the first one indicates your shoe size.

Yes, the trick is designed to give a two-digit answer using algebra.

For example, my shoe size is 7.

Multiply 7 by 5: 5x7=35

Add 50: 35 + 50 = 85

Multiply the result by 20: 85x20=1700

Add 1019: 1700 + 1019 = 2719

Subtract year of birth: 2719 – 1994 = 725

So we got it, the first digit is 7 – my shoe size as we already know. And the other two digits show my age, 25 (fact).

The 1089 Trick

Pick a random number that has 3 digits.

Put the largest digit first and the smallest last (descending order).

Now do the opposite then subtract the new number from the result in the step above.

Next, reverse the order of the answer’s digits.

Add the newly rearranged number to the answer from the last step and you’ll get 1089!

For instance, I pick 237.

In descending order, we have 732.

In ascending order, we have 237, 732 – 237 = 495

After reversing, we have 594.

Lastly, 594 + 495 = 1089!

1, 2, 4, 5, 7, 8 Trick

Pick a random number from 1 to 6.

Multiply it by 9.

Multiply the answer by 111.

Then multiply the result by 1001.

Next, divide the answer by 7.

Eventually, you get an answer containing the numbers listed in the title, 1, 2, 4, 5, 7, and 8.

Single Digit Numbers Math Trick

First, think of 2 random single-digit numbers.

Next, pick one of them and multiply by 2.

Now add 5 to the answer.

Then add the other number to the answer above.

Subtract 25 from the result.

The final answer will contain the 2 number you thought of at first.

It's always 2

Choose a random number and multiply by 3.

Add 6 to the result.

Divide the answer above by 3.

Subtract the initial number from the result and you’ll get 2.

For instance, I choose 125, 125 x 3 = 375

375 + 6 = 381

381/3 = 127

127 – 125 = 2

It's always 5

Pick a random number then multiply it by 2.

Add 10 to the answer.

Divide the result by 2.

Subtract the original number from the answer above and you’ll get 5.

Tip to Remember Pi

As Pi is an irrational number, we cannot learn all the digits behind the decimal point. However, we can memorize the first few digits to use when calculating something. Remember this sentence, “How I wish I could calculate pi.”

Each word’s number of letters represents each digit, meaning 3.141592.

Multiply by 6

When you multiply any even number by 6, the last digit of the result will be the number you used to multiply, and the tens digit will be half of the ones digits.

For example, 6 x 4 = 24.

Three digits the same trick

Pick a number with three digits where all of them are the same, for example, 222 or 555.

Add the digits together.

Now divide the original number by the result from above, and you’ll get 37.

For example: with the number 22, we have 2 + 2 + 2 = 6. 222/6 = 37.

The 11 Rule

We all know the “10 Rule”, meaning when you multiply a number by 10, you simply add a 0 to that number's end. But now everyone knows the 11 rule, where you multiply two-digit numbers by 11.

For example, let’s multiply the number 52 by 11.

First, split the two digits (5_ _ 2).

Then add them together (5+2=7).

Next, place the result between the digits (6 7 2).

You got it, 11 x 52 = 572. Easy right?

However, the tricky part here is when adding the two digits gives you a number greater than 9, you put the “ones” digit between the two digits of the initial number and add the “tens” digit to the first digit of the initial number, as in the following example.

11 x 67 … 6 __ 7 … 6 + 7 = 13

Now, put 3 between 6 and 7. Then, add 1 to 6 which results in 7. And the answer is 737.

11x 67 = 737