SSC CGL 2020 Preparation: Quantitative Aptitude

The SSC CGL 2020 strategy for the quantitative aptitude section should be detailed enough because the clarity of concept is a must for this section while doing SSC CGL 2020 Preparation.  

Percentage

The Percentage (%) is a term which represents the part of a number or quantity in term of the fraction of 100.

(x * n)/100

Basic Properties & Formulas:

a. For a given x and n 

n% of x= x% of n

b. If the number n is increased or decreased by x, then the change in percentage can be defined as 

               x (1+ n/100)

c. If there is a correction in any value or number, then the percentage change can be represented by the formula:  

Percentage change in value= (change/initial value)*100 

Here, Change= final value- initial value

1. When the value is increasing or decreasing with the rate of R% annually. Then,

Value after n years = P*(1 + R/100) n

Value before n years = P/ (1 + R/100) n

Example: What is the percentage change in the price of a commodity if the price of the commodity increased to Rs 150 from Rs 100?

Solution: Change in price= 150-100

 = Rs 50 

Percentage Change in Price= (change/initial value)*100

   = (50/100)*100

   = 50 %

Ratio and Proportion

Ratio is the way of representing a number in terms of another number. It will be represented in the form of (p/q).

1. Here the order of elements cannot be changed when representing ratio. 

x: y ≠y: x

Example: The population of a city is 50,000. Of the total population, there are 30,000 males. Find out the ratio of the number of males to the number of females in the city? 

Solution: Number of Females in the city

= Total Population- Number of Males

= 50000-30000

= 20000

Ratio of the number of Male to Female

= Number of Males/ Number of Females

= 30000/20000

 =3/2

Ratio of Number of Male to female= 3:2 

Proportion is a way of representing the equal ratios of different elements together. It is denoted by the symbol::.

X: Y:: A: B

Example: Find the value of x defined in the following proportion 2: x:: 3:9

Solution: Given 2: x:: 3:9

2/x= 3/9

After cross multiplication we find,

 2*9 = 3*x

3*x= 18

x= 18/3

x= 6

Square Roots

1. The square root (√) of a number is represented in terms of the number multiplied by it. It is the inverse of the square.

Short Trick:

a. Find the two closest square numbers from the number of which you want to calculate the square root.

b. Divide the number with the lowest square number out of 2.

c. Take the average of division and lowest square number.

d. Repeat the steps 2 and 3 till you get the value of average exceeding the highest closest square number.

e. The whole number you get from the last average will be your answer.

Example: Find the value of √16?

Solution: Let x=16

The two closest square numbers are 32=9 and 52= 25 

X1= x/3=16/3= 5.33

X2= (3+5.33)/2= 4.165

X3= x/4.165= 16/4.165= 3.841

X4= (x2+x3)/2= (4.165+ 3.841)/2= 4.003

X5= x/x4= 16/ 4.003= 3.997

X6= (x4+x5)/2=(4.003+3.997)/2= 4 

√16= 4

All The Best To All The SSC CGL 2020 Aspirants