Speed Maths 1 | Arithmetic | Quantitative
Aptitude | CAT PREPARATION 2021
Rodha
Speed Maths: Percent Approximation
Hi everyone, my name is Ravi Prakash and welcome to the first
class of Speed Maths. In this class, we will be discussing percent
approximation, a very important topic in quantitative and data
interpretation. We will learn how to calculate percentage
approximation in maximum ten seconds. Let's start!
Understanding Percentages
Before we dive into percent approximation, it's important to
understand how to calculate basic percentages. For example, if
we take the number 648, we should be able to calculate 10%,
5%, 1%, 25%, 75%, and 50% of this number. These calculations
should be done mentally.
To calculate 10%, simply move one decimal point back. For
example, 10% of 648 is 64.8.
To calculate 5%, remember that it is half of 10%. So, 5% of 648
is half of 64.8, which is 32.4.
To calculate 1%, move two decimal points back. So, 1% of 648
is 6.48.
To calculate 25%, remember that it is one-fourth of the
number. You can either double and halve the number twice or
directly calculate one-fourth of it. For example, 25% of 648 is
162.
To calculate 75%, you can either treat it as 100% minus 25% or
calculate 25% of the number and multiply it by 3. For example,
75% of 648 is 486.
Percent Approximation Example
Let's take an example to understand percent approximation
better. What is 16% of 1234?
One way to approach this is to break down 16% into 10%, 5%,
and 1%. We already know that 10% of 1234 is 123.4 and 5% is
Aptitude | CAT PREPARATION 2021
Rodha
Speed Maths: Percent Approximation
Hi everyone, my name is Ravi Prakash and welcome to the first
class of Speed Maths. In this class, we will be discussing percent
approximation, a very important topic in quantitative and data
interpretation. We will learn how to calculate percentage
approximation in maximum ten seconds. Let's start!
Understanding Percentages
Before we dive into percent approximation, it's important to
understand how to calculate basic percentages. For example, if
we take the number 648, we should be able to calculate 10%,
5%, 1%, 25%, 75%, and 50% of this number. These calculations
should be done mentally.
To calculate 10%, simply move one decimal point back. For
example, 10% of 648 is 64.8.
To calculate 5%, remember that it is half of 10%. So, 5% of 648
is half of 64.8, which is 32.4.
To calculate 1%, move two decimal points back. So, 1% of 648
is 6.48.
To calculate 25%, remember that it is one-fourth of the
number. You can either double and halve the number twice or
directly calculate one-fourth of it. For example, 25% of 648 is
162.
To calculate 75%, you can either treat it as 100% minus 25% or
calculate 25% of the number and multiply it by 3. For example,
75% of 648 is 486.
Percent Approximation Example
Let's take an example to understand percent approximation
better. What is 16% of 1234?
One way to approach this is to break down 16% into 10%, 5%,
and 1%. We already know that 10% of 1234 is 123.4 and 5% is
