Top Five Math Tricks and Their Use

Mathematics is one of the difficult disciplines at any level of learning. Most of us usually wish it should not be taught beyond basic additions and subtractions. Last week I visited united college to teach them calculus and all I met was sleepy and unmotivated students. I learnt through their teacher that they seriously dread mathematics. However, learning some basic math tricks could be of great help. Some of these simple tricks are:

Is a number divisible by 3?

As a general rule, when a number is evenly divisible by another number, it is said to be a multiple of that number e.g. because 36 is evenly divisible by 3, 36 is a multiple of 3. Also, if the sum of individual digits of a number is a multiple of 3, that number is evenly divisible by 3.

Example:

429 is divisible by 3 since 4+2+9=15 whereby 15 is a multiple of 3.

Multiplying by 9

Raise your hands with all your fingers spread. In order to multiply 5 by 9, bend your fifth finger from left and count your fingers to the left – you should get 4. Then count fingers to the right – you should get 5. The answer is answer is 45. This works for numbers below 10.

Also, when multiplying a number by 9, you multiply it by 10 then subtract the number.

Example:

16×9=144

16×10=160

160-16=144

Still, in multiplication tables of 9, the answer digits add up to 9.

Example:

16×9=144

(1+4+4)=9

Multiplying by 12

Let’s take a multiplication of 9 by 12. Multiply 9 by 10 then 9 by 2 and add the two answers.

Example:

9×12= 108

9×10=90

9×2=18

90+18=108

Also, you can use 12 as a sum of 10 and 2.

Example:

35×12=420

35x (10+2)

(35×10) + (35×2)

350+70=420

Multiplying by 4

The trick is simple. Multiply a number by 2 then double your answer i.e.

30×4

30×2=60

60×2=120

30×4=120

The trick works since;

2×2=4

Therefore;

30×4=30x (2×2)

So, 30x2x2

60×2

120

Multiplying by 11

When you multiply any number by 11 e.g. 34, the first digit of the answer is the first digit of that number i.e. 3 and the last digit of the answer is still the last digit of that number i.e. 4. To get the digit between the two digits, add 3 and 4.

Example:

34×11=374

34×11=3 (3+4) 4

If you get a two digit number after adding up the two digits, you should do this;

93×11

9 (9+3) 3

9 (12) 3

(9+1) 23

1023

The issue here is the place value; multiply 93 by 1, then by 10 and adding the two products.

Example:

93×1

93×10

93+930=1023

Mastering these tricks will enable you to do such multiplication in simple manner. I recommend that you master and device other math tricks to enable you to tackle math problems with ease, won’t you?

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