5 Fun Math Tricks To Make Your Life So Much Easier
Let's be honest – mathematics isn't exactly Mr. Popularity when it comes to everyone's favorite school subject, and that mentality even extends beyond the classroom. When's the last time you saw an adult whip out a pad and pencil to add up some basic sums or do a little multiplication? It's probably been a few decades, or at least since before electronic calculators became a household staple. But there may be times when you don't have access to a calculator, and there will definitely come a time when your children or younger family members will ask you to help them with their math homework, so if you don't want to get caught with egg on your face, it's time to get back to basics, and there's no better way to do that than with these simple math tricks that will make math fun again!
1. Multiply by 7
As a small learning exercise – and to help memorize the 7 times table – first draw a grid with nine fields, just like one you would make for tic-tac-toe. Now label the boxes. In the far-right top box, write the number 1. In the far-right center box, write the number 2. In the far-right bottom box, write the number 3. In the middle top box, write the number 4. In the middle center box, write the number 5. In the middle bottom box, write the number 6. In the far-left top box, write the number 7. In the far-left center box, write the number 8. In the far-left bottom box, write the number 9.
Write the numbers 0-6 individually on separate strips of paper, and the numbers 2 and 4 will appear twice (in the end you should have 9 tiles as such: 0, 1, 2, 2, 3, 4, 4, 5, 6). Now arrange these tiles as shown in the picture below. Do you notice all the striking patterns here? First off, this is this a multiplication table for the number 7 – notice the complete boxes from the top left corner, going from left to right: 7, 14, 21, 28, 35, 42, 49, 56, and 63 – all multiples of the number 7! It is also striking that the tiles are arranged in ascending order horizontally from left to right and from top to bottom, while the written numbers in the grid are arranged numerically from top to bottom and from right to left. Isn't math great?!
2. Find the Square Number
Finding the square number can be a serious pain, and who can keep up with all that long multiplication? Make your life so much easier with this easy hack that only requires two steps. First add the entire number you want to find the square number of (in this case: 104) to the last digit of the entire number (in this case: 4) and this will give you: 104 + 4 = 108. In the second step, multiply the last digit by itself (in this case: 4 x 4 = 16) and write this number (16) down after the first answer (108), and tada, you have your answer: the square number of 104 is 10,816! While this is a pretty cool trick, you should note that in this form, it only works for the numbers 11 to 13 and 104 to 109, so be sure to keep that in mind the next time you need to find the square number.
3. Multiply by 9
This trick is the easiest of them all, and thank goodness for that because the 9 times table is the quite possibly the hardest to recite from memory alone. All you have to do is put both of your hands with the palms facing up in front of you – the thumb on your left hand is 1, the index finger on your left hand is 2, the middle finger on your left hand is 3, and so, counting from left to right, all the way until the thumb on your right hand which is 10.
Now for the trick: simply fold in the finger you want to multiply by 9! The folded finger works as a stopping point, so however many fingers there are before the folded finger is the first digit, and however many numbers after the folded finger is the second digit. For example, if you want to multiply 9 X 1, you fold in the thumb on your left hand (the 1st finger) – there are 0 fingers before the folded finger, and 9 fingers after the folded-in finger, so the answer is 09. If you want to multiply 9 x 5, you fold in the pinkie on your left hand (the 5th finger) and are left with 4 fingers before the folded finger and 5 fingers after the folded finger. Put them together and what do you get? 45! And 9 x 5 is indeed 45.
And just one more example to make sure you've got the hang of it: multiply 6 x 9. Count to the 6th finger, which is the pinkie on your right hand, and fold it in. And what do you have? 5 fingers before the folded finger and 4 fingers after the folded finger, giving you 54. What a neat trick!
First a little refresher: when you multiply two numbers, the first number is the known as the multiplier and the second number is known as the multiplicand. So when multiplying 314 x 7, the multiplier is 314 and the multiplicand is 7. So that we have that cleared up, on to the trick!
This trick works with any ol' number: draw a table in which each digit of the multiplier (in this case: 314) gets its own column, and each digit of the multiplicand (in this case: 7) gets its own row. The fields are then halved diagonally as shown. Then draw a diagonal line through each box as shown in the picture below, making sure to extend the lines slightly past the bottom of the boxes.
Starting from the left, multiply the first digit of the multiplier by the multiplicand (in this case: 3 x 7). Then write the answer in the first box on the left. The box has been split in two so you can write one digit in each half. For example, the answer is 21, so the 2 goes in the top half of the far-left box and the 1 goes in the bottom half of the far-left box. Repeat this with the rest of the numbers.
When the table is filled, add the numbers that are diagonal to each other and note these totals below the table. And voilà, you have your answer!
If your multiplicand is a two-digit number, carry on as usual, but when adding the diagonal digits, you need to add the tens digit to the addition result of the diagonal to the left of it.
5. Divide by 9
Divide each number by 9 by taking the following notes below the dividend (the number to be divided). First, note the first digit of the dividend that remains. In the second place, write down the sum of the first and the second digit of the dividend. In the third place, note the sum of the addition result just listed and the third digit of the dividend. And so on and son: the last quoted number is added to the next digit of the dividend.
In the end, you'll have a number that is the sum of your last noted number and the last digit of the dividend. You divide this remaining number by 9 and add the result to the last digit.
If the numbers you write down below the dividend are double digits, add the tens digit to the number to the left of it. If the last remaining number is not divisible by 9, take the remainder 10 times and divide it by 9 – also repeat this with the resulting remainder. These are then the decimal places of the final result, which are usually infinite.
If you're a big math fan, you might already be familiar with some of these tricks and they're more of a fun hobby than a quick hack. Whether this was a refresher or you learned a whole new bunch of tricks, it's always fun to put your brain to use, which is always time well spent. And now you can bust out your newfound skills at the next get-together and impress everyone around you, because who needs an electronic calculator when you've got a human calculator handy?