5 Arithmetic Tricks for Children
- Aug 23, 2016
- Sudipto Das
Many children have the tendency of neglecting their basic arithmetic operations when they are at an early stage of their career. The result can be pretty disastrous especially in the long run when they enter into the world of advanced mathematics. Hence, it can easily be said that students must know their basic arithmetic pretty well to benefit in the long run starting from memorizing multiplication tables to arithmetic tricks.
Now you are probably wondering whether math tricks are good or not. Before answering that question, we’ll ask you a question first. What do you reckon of a situation where your child has come to know of a quicker way to multiply certain numbers? Surely, you’ll be pleased with that because that’s undoubtedly a positive math approach. Well, arithmetic tricks serve the exact same purpose; make your child figure out quicker ways to operate. Therefore, we can say that arithmetic tricks are undoubtedly good for your child. We have provided you with 5 of these tricks that should benefit your child in the long run. Let’s begin.
1. Multiplication by 4
It is one of the simplest tricks of all but undoubtedly it’s pretty effective. To multiply any number by 4, multiply the same number by 2 first and then multiply the product you found with 2 again.
45 x 4= 180.
45 x 2= 90.
90 x 2= 180.
So why does it work?
It works because of a simple reason that 2 x 2=4. You are just breaking the number 4 into two easier parts (2 x 2) and applying the same to your math operation.
So the basic underlying principle of the “trick” is that you can solve any multiplication problem by multiplying by its factors.
2. Multiplication by 9
It’s known as the mysterious finger trick and it’s suitable for all numbers between 1 to 10 that are to be multiplied by 9.
Say for example you have to multiply 4 x9. Spread your fingers on both hands. Now start from the left, and count 1, 2, 3, 4 and STOP. Bend that 4th finger. You have the answer right in front of you. Take a look at the image below.
According to the image above, count the number of fingers to the left of your bent finger. It should be 3.
After that, count the number of fingers to the right of your bent finger (including both the hands). It should be [1 (left hand) + 5 (right hand)] 6.
So how does it work?
When you are multiplying a number by 9, you can actually multiply the same by 10 and subtract the same number
As per this rule, it should be: 4 x 9
= 4 x (10 -1)
= 4x 10 - 4 x1= 36.
So, now you can apply the same rule to your mysterious finger trick. When you are asked to multiply a number(x) from 1 to 10 with 9, count from the left and bend your xth finger down. The combination of the number of fingers to the left of x and to the right of x should be your result.
3. Multiplication by 11
Multiplication a number by 11 is pretty easy.
But do you actually know that there is one trick through which you can multiply any 2 digit number with 11? The process is explained below with an example:
Say, 52 x 11
The 1st digit of the result will be the 1st digit of the number that has to be multiplied and the last digit of the result is the 2nd digit of the number that ahs to be multiplied. And the digit in between the 1st and then last digit of the result can be found out by getting the sum of the 1st and 2nd digit of the number that has to be multiplied.
52 x 11
The trick becomes a little tricky when the sum of the numbers in between becomes a 2 digit number itself. For that, let’s come to this 2nd example:
87 x 11
= 8(8+7) 7
4. Multiplication by 12
Similar to the previous trick, you can multiply any number with 12 using this trick. Take a look at the examples below.
24 x 12
24 x 10= 240
24 x 2= 48
So why does it work?
You are actually breaking the number 12 into two easily calculable numbers- 10 and 2.
Now let’s look into the operation:
24 x (10+2)
= 24 x 10 + 24 x 2
= 240 + 48
5. Check whether a number is divisible by 3 or not
Take a peek at the example below:
Check whether the number 543 is divisible by 3 or not.
Get the sum of the digits (5+4+3= 12).
Since 12 is divisible by 3,
The number 543 is easily divisible by 3.
There are several other tricks on the internet or in some very special books that deal exactly in this topic. You can check those out for your kids. You can also consult a professional math tutor who can do this job for you. That should be all for now. Hope you had a good read.
Sudipto writes technical and educational content periodically for wizert.com and backs it up with extensive research and relevant examples. He's an avid reader and a tech enthusiast at the same time with a little bit of “Arsenal Football Club” thrown in as well. He's got a B.Tech in Electronics and Instrumentation.
Follow him on twitter @SudiptoDas1993
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