Quantative Aptitude: Percentage & Its Concepts

Percentage 

Percentage is per-cent which means parts per hundred

Percent sign

The percent sign is the symbol: %

It is written to the right side of the number: 50%

Percentage Definition

Percentage is a value that represents the proportion of one number to another number.

1 percent represents 1/100 fraction.

If we have to convert percentage into fraction than it is divide by 100.

Example 1 :- if we write 45% then its equal to 45/100 or in fraction 9/20 or in decimal 0.45

if we have to convert fraction into percentage we have to multiple with 100.
Example 2 :- if we write 3/5 in fraction it is equal to 60%

 3/5x100=60.

Convert Percentage into Decimal:

 20% = 20/100 = 0.5

Convert Decimal Into Percentage:

0.25 = (0.25 × 100)%  = 25%

1.50 = (1.50 × 100)% = 150%

Here is a table of commonly used values shown in Percent, Decimal and Fraction form:

Percent	Decimal	Fraction
1%	0.01	1/100
5%	0.05	1/20
10%	0.1	1/10
12½%	0.125	1/8
20%	0.2	1/5
25%	0.25	1/4
331/3%	0.333...	1/3
50%	0.5	1/2
75%	0.75	3/4
80%	0.8	4/5
90%	0.9	9/10
99%	0.99	99/100
100%	1
125%	1.25	5/4
150%	1.5	3/2
200%	2

Type of  question that has been always asked in the exams.

Type : 1: 65g is what per cent of 2 kg? (CGL-2008)

(a) 13/4                               (b) 35/2

(c) 15/8                               (d) 13/8

Answer (a) Required percentage = (65/2000) ×100=13/4

Type : 2: If 90% of A =30% of B and B=x% of A, then the value of x is ( CGL – 2011)

(a) 800                                 (b) 300

(c) 700                                  (d) 400

Answer: (b) A × 90/100=(B×30)/100

A x 3 = B

A x x% = A x 3

x/100=3 =x=300

Type :3:  Given A is 50% larger than C and B is 25% larger than C, the A is what percent larger than B? (CGL-2013)

(a) 25%                               

(b) 50%

(c) 75%                               

(d) 20%

Answer:(d)Let C = 100 then  A = 150 , B = 125

(150-125)/125×100=20%

Type : 4:  Radha spends 40% of her salary on food, 20% on house rent, 10% on entertainment and 10% on conveyance. If her savings at the end of a month are Rs. 1500, the her salary per month (in Rs.) is                    (CGL-2003)

(a) 8000                               (b) 7500

(c) 6000                               (d) 10000

Answer (b) Radha’s total percentage expenditure = (40 + 20 + 10 + 10)% = 80%

Percentage savings = 100-80=20%

Now, 20% of her total salary = 1500
So, 1% of her salary will be = 1500 / 20 = 75.
Hence her salary = 100% = Rs 7500

Type5: If the numerator of a fraction is increased by 20% and the de-nominator is decreased by 5%, the value of the new fraction becomes 5/2. The original fraction is-  (CGL – 2005)

(a) 24/19                             (b) 3/18

(c) 95/48                             (d) 48/95

Answer: (c) Let original fraction by x/y

According to the question,

(120/100 x)/(95y/100)=5/2

=120x/95y=5/2

x/y=5/2 × 95/120=95/48

Her total salary = (1500×100)/20 = Rs. 7500

Type6: Two numbers are respectively 20% and 50% of a third number. What percent is the first number of the second? (CGL-2002)

(a) 10%                                (b) 20%

(c) 30%                                (d) 40%

Answer: d) Let the third number be x,

According to the questions:

First number = 20/100 × x=x/5

Second number = 50/100 × x=x/2

Required percentage

= (x/5×100)/(x/2) =x/5×2/x×100 = 40%

Type 7: A reduction of 20% in the price of oranges enables a man to buy 5 oranges more for Rs. 10/-. The price of an orange before reduction was: ( CGL – 2000)

(a) 20 paise             (b) 40 paise

(c) 50 pasie                         (d) 60 pasie

Answers: (c) 20% of Rs. 10 = 20/100 ×Rs.10=Rs.2

Reduced price of 5 oranges = Rs. 2

Reduced price of 1 orange = (Rs.2)/5=200/5  paise  = 40 paise

Original price of 1 orange  = 40/(1-0.20)=40/0.8=400/8 = 50 paise

Type8: In an examination, 65% of the students passed in Mathematics, 48% passed in Physics and 30% passed in both. How much per cent of students failed in both the subjects? (CGL- 2007)

(a) 17%                                (b) 43%

(c) 13%                                (d) 47%

Answer: (a) n (M) = 65, n (P) = 48, n (MÇP)=30

\ n (MÈP) = n (M) + n (P) – n (MÇP)

= 65+48-30=83

 Percent of students passed = 83

 Percent of students failed = 17

Or, Student passed only in Math = 65-30 = 35%

Students passed only in Physics = 48 -30 = 18%

total pass = 35 + 18 +30 = 83%

 35 + 18 + 30 = 83%

 Failed = 100-83=17%

Type 9: A number is increased by 20% and then it is decreased by 10%. Find the net increase or decrease per cent.

(a) 10% increase              (b) 10% decrease

(c) 8% increase                 (d) 8% decrease

Answers: (c) Net % change = A + B + AB/100

Here, A = 20%, B = - 10%

Net % change = 20 – 10 – 200/100 = 10 – 2 = 8% +ve sign shows increase

Type10: In an election between two candidates, 75% of the voters cast their votes, out of which 2% votes were declared invalid. A candidate got 9261 votes which were 75% of the valid votes. The total number of voters enrolled in that election was  ( CGL – 2003)

(a) 16000                            (b) 16400

(c) 16800                            (d) 18000

Answer (c) Let the total number of voters enrolled be x.

Number of votes polled = 75% of x = 3x/4

= 3x/4-2/100 × 3x/4=3x/4-*3x/200=147x/200

Now, 75% of 147x/200=9261

Or, 3/4 of 147x/200 = 9261

Or, x = (926×4×200)/(3×147)=16800