Ace questions on percentage for SI exams
Hyderabad: This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some previously asked questions and answers along with explanations on the percentage topic. 1) The population of a town is 1,54,000. It increases by 5% during the first year. During the second year it […]
Hyderabad: This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some previously asked questions and answers along with explanations on the percentage topic.
1) The population of a town is 1,54,000. It increases by 5% during the first year. During the second year it decreases by 10% and increases by 10% during the third year. Then the population of the town after three years is(SI 2016)
a) 161700 b) 160700 c) 160083 d) 170062
Ans: c
Explanation:
The population of a town = 1,54,000
The population of a town after 3 years = = 160083
∴the population of the town after 3 years is 160083.
2) A number x is increased by 30% and then decreased by 30%, then the number x is (SI 2016)
a) Does not change b) decreases by 6%
c) Increases by 6% d) decreases by 9%
Ans: d
Explanation:
Since we have given that a number is increased by 30%.
Then a number is decreased by 30%.
Let x = 30% and y = -30%
So, the net increase or decrease percent would be
Hence, there is net decrease of 9%.
3) One side of a square is increased by 20%. To maintain the same area the
other side will have to be decreased by(SI 2016)
a) 16 2/3% b) 14 2/3% c) 11 1/3% d) 14 1/3%
Ans: a
Explanation:
Suppose size of square = 100
Area= 100×100= 10000
Now, 20% increase in size would be =(20% of 100)=20
New length of square = 100 20=120
To maintain the original area i.e 10000
10000= 120 x new size of another side
= 10000/120= 83.33
So decrease must be of (100–83.33)= 16.66
Percentage decrease is= 16.66% or 16 2/3%
4) Two numbers are in the ratio 5: 4. If 40% of the first number is 120, then 60% of the second number is equal to(SI 2016)
a) 124 b) 134 c) 144 d) 156
Ans: c
Explanation:
Two numbers are say 5x and 4x.
40% of 5x = 120, or
(40/100)*5x = 120
Or x = 12000/200 = 60.
Hence 60% of the second number = 0.6*4*60 = 144
5) In an examination there were 640 boys and 360 girls. If 60% of boys and 70% of girls were successful, the percentage of failure was(SI 2016)
a) 36.4% b) 35.4% c) 32.8% d) 35.6%
Ans: a
Explanation:
Total number of students = 640 360 = 1000
Number of successful boys = 60% of 640 = 384
Number of successful girls = 70% of 360 = 252
Total number of successful students = 384 252 = 636
Number of unsuccessful students = 1000 – 636 = 364
∴required percentage= 364/1000×100=36.4%
6) A person gave 20% of his income to his elder son, 30% of the remaining to the younger son and 10% of the balance he donated to a trust. If he is left with Rs. 10080. His income ( in rupees) is(SI 2016)
a) 50000 b) 40000 c) 30000 d) 20000
Ans: d
Explanation:
Let us assume he had Rs. x.
Finally left amount = (100 – 20)% of (100 – 30)% of (100 – 10)% of x = 10080
10080
x = 10080
x = 20,000
7) In a school, the ratio of the number of boys and girls is 3:2. If 30% of the boys and 20% of the girls are scholarship holders, then the percentage of students that do not get scholarship is(SI MAINS 2018)
a) 80 b) 74 c) 20 d) 26
Ans: b
Explanation:
Let there be 100 students.
Then number of boys =3/5×100=60
Number of girls =2/5×100=40
Total scholarship holders =30 % of 60 20 % of 40 = 18 8=26
Number of students without scholarship =100−26=74
∴% of students without scholarship =74/100×100=74 %
DIRECTIONS FOR 8 and 9:
Read the data given in the table below and answer questions 2 and 3.
School No. of students passing in the examination Pass percentage of the students
P 360 20
Q 520 80
R 540 90
S 420 70
8) The total number of students appears in the examinations is(SI MAINS 2018)
a) 1840 b) 2400 c) 3200 d) 3650
Ans: d
Explanation:
Total number of students in school P =360/20×100=1800
Total number of students in school Q =520/80×100=650
Total number of students in school R =540/90×100=600
Total number of students in school S =420/70×100=600
Total students= 1800 650 600 600= 3650
9) The total number of students who failed in the examinations from the schools Q, R and S is(SI MAINS 2018)
a) 370 b) 320 c) 260 d) 240
Ans: a
Explanation:
Total number of failed students in school Q = 650-520=130
Total number of failed students in school R= 600- 540=60
Total number of failed students in school S= 600-420=180
Total = 130 60 180=370
10) If A earns 50% more than B and B earns x% less than A then x=?(SI MAINS 2018)
a) 66 2/3% b) 33 1/3% c) 50 d) 25
Ans: b
Explanation:
According to question:
A earns 50% more than B
Let B=100
Then A=150
According to question how much is B less than A
A=150, B=100
Required percentage = = 33.33%
Finally you answer= 33.33%, B less than A
Banda Ravipal Reddy,
Director, SIGMA,
SaiInstitute of General Mental Ability,
Hyderabad.
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