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Aptitude - Percentage

Exercise : Percentage - General Questions
6.
If 20% of a = b, then b% of 20 is the same as:
4% of a
5% of a
20% of a
None of these
Answer: Option
Explanation:

20% of a = b      20 a = b.
100

b% of 20 = b x 20 = 20 a x 1 x 20 = 4 a = 4% of a.
100 100 100 100

7.

In a certain school, 20% of students are below 8 years of age. The number of students above 8 years of age is of the number of students of 8 years of age which is 48. What is the total number of students in the school?

72
80
120
150
100
Answer: Option
Explanation:

Let the number of students be x. Then,

Number of students above 8 years of age = (100 - 20)% of x = 80% of x.

80% of x = 48 + 2 of 48
3

80 x = 80
100

x = 100.

Video Explanation: https://youtu.be/yPfocU6DA2M

8.
Two numbers A and B are such that the sum of 5% of A and 4% of B is two-third of the sum of 6% of A and 8% of B. Find the ratio of A : B.
2 : 3
1 : 1
3 : 4
4 : 3
Answer: Option
Explanation:

5% of A + 4% of B = 2  (6% of A + 8% of B)
3

5  A + 4  B = 2 6  A + 8  B
100 100 3 100 100

1  A + 1  B = 1  A + 4  B
20 25 25 75

1 - 1  A =  4 - 1  B
20 25 75 25

1  A = 1  B
100 75

A = 100 = 4 .
B 75 3

Required ratio = 4 : 3

Video Explanation: YouTube Video

9.
A student multiplied a number by 3 instead of 5 .
5 3

What is the percentage error in the calculation?

34%
44%
54%
64%
Answer: Option
Explanation:

Let the number be x.

Then, error = 5 x - 3 x = 16 x.
3 5 15

Error% = 16x x 3 x 100 % = 64%.
15 5x

10.
In an election between two candidates, one got 55% of the total valid votes, 20% of the votes were invalid. If the total number of votes was 7500, the number of valid votes that the other candidate got, was:
2700
2900
3000
3100
Answer: Option
Explanation:

Number of valid votes = 80% of 7500 = 6000.

Valid votes polled by other candidate = 45% of 6000

= 45 x 6000 = 2700.
100

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