Mathematics Shortcuts: Percentage (Part 1)

Mathematics Shortcuts: Percentage (Part 1)

Greeting Aspirants,

We have discussed some pretty useful mathematical tricks in the previous articles. Like, Cube-roots, Squaring, Simple Interest, Compound Interest and Time and Work. In case you have missed out on them, we strongly recommend you to go through them.

In this article, we will learn how to quickly solve percentage related problems that are quite common in exams like SSC, Banking, Railways etc. This is a 3 part article, in this part, we will the basics of percentage and how to calculate simple percentage problems mentally.

First of all, What is the percentage?

Percent, as the name suggests, means “Per Cent” i.e. for every 100. Which means, when you are calculating the percentage of a value you are actually calculating the value for every 100 of the reference value. So, when you see the percentage symbol “%” you should know that it means divided by 100. For Example- 11% means 11/100.

Moving on, let’s learn how to calculate simple percentage problems mentally.

To do this, we have to memorize some basic percentage analogies. For example, when you have to find 50% of a value, you know in your head that 50% means half of the value, so you mentally half the given value and you get your answer.

Similarly,

1. 100 % of a number is the number itself.

2. 50 % of a number is half of it.

3. 25 % of a number is one-fourth of the given number.

4. 10 % of a number is equal to the number divided by 10.

5. 5 % of a number is half of 10 %.

Using this, we can solve a wide variety of basic problems

Question: What is 15 % of 620?

Solution:

Normally, we use BODMAS to solve these problems

i.e. 15 % of 620 = 15/ 100 x 620

Now, this is easy, no doubt about that. But you certainly cant do that in your head.

How To Calculate this in Head?

It’s Simple, break down 15 % into simpler forms of 10 % and 5 %

15% = 10% + 5%

Now, we know

10 % of 620 will be 620 divided by 10.

i.e. 10% of 620 = 62 (Anyone can do it in their head)

also 5% of 620 = half of 10% of 620 = 31

So, 15% of 620 = 10% of 620 + 5% of 620 = 62 + 31 = 93

Let’s try another one (Try to solve it in your head)

Question: What is 55 % of 350?

Solution: 55% = 50% + 5%

50% of 350 = Half of 350 = 175

5 % of 350 = Half of 10% of 350 = Half of 35 = 17.5

Hence,

55% of 350 = 175 + 17.5 = 192.5

Note: Solve as many problems as u can because this is just a tiny part of a Giant topic Percentage.

All the Best!!

OT Team