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

Answer: Option A

Explanation:

Let the number be x,
then,
$$\begin{aligned} \frac{5}{3} - \frac{3}{5} = \frac{16}{15}x \end{aligned}$$

Error% = $$\begin{aligned} (\frac{16}{15}x * \frac{3}{5} * 100)% = 64% \end{aligned}$$

Answer: Option D

Explanation:

Let their marks be (x+9) and x.
Then, x+9 = 56/100(x + 9 +x)
=> 25(x+9)
=> 14 (2x + 9)
=> 3x = 99
=> x = 33.
So, their marks are 42 and 33

Answer: Option C

Explanation:

Failed in mathematics, n(A) = 34
Failed in English, n(B) = 42
$$\begin{aligned} n(A\cup B) = n(A)+n(B)-n(A\cap B) \\ = 34+42-20 = 56 \\ \text{Failed in either or both subjects are 56} \\ \text{Percentage passed = }(100-56)\% \\ = 44\% \end{aligned}$$

Answer: Option C

Explanation:

While calculation in terms of percentage we need to multiply by 100, so
2.09 * 100 = 209.

Answer: Option C

Explanation:

Actually it means 5 is what percent of 20, which can be calculated as,
(5/20)*100 = 5 * 5 = 25