1. Total number of boys and girls in a school is 150. If the number of boys is x, then girls become x% of the total number of students. The number of boys is
50
60
70
80
Answer: Option B
Explanation:
Clearly,
x% of 150 = 150 - x [as x is number of boys]
\begin{aligned}
=> x + \frac{x}{100} * 150 = 150 \\
=> \frac{5}{2}x = 150 \\
=> x = 60 \\
\end{aligned}
2. 10% of inhabitants of a village having died of cholera, a panic set in, during which 25% of the remaining inhabitants let the village. The population is then reduced to 4050. Find the original inhabitants
5500
6000
6500
7000
Answer: Option B
Explanation:
Let the total number is x,
then,
(100-25)% of (100 - 10)% x = 4050
=> 75% of 90% of x = 4050
=> 75/100 * 90/100 * x = 4050
=> x = (4050*50)/27 = 6000
3. If 15% of 40 is greater than 25% of a number by 2, the number is
14
16
18
20
Answer: Option B
Explanation:
15/100 * 40 - 25/100 * x = 2 or x/4 = 4 so x = 16
4. In an examination, 34% of the students failed in mathematics and 42% failed in English. If 20% of the students failed in both the subjects, then find the percentage of students who passed in both the subjects.
40%
42%
44%
46%
Answer: Option C
Explanation:
Failed in mathematics, n(A) = 34
Failed in English, n(B) = 42
\begin{aligned}
n(A\cup B) = n(A)+n(B)-n(A\cap B) \\
= 34+42-20 = 56 \\
\text{Failed in either or both subjects are 56} \\
\text{Percentage passed = }(100-56)\% \\
= 44\%
\end{aligned}
5. 2.09 can be expressed in terms of percentage as
2.09%
20.9%
209%
0.209%
Answer: Option C
Explanation:
While calculation in terms of percentage we need to multiply by 100, so
2.09 * 100 = 209.