2.09 can be expressed in terms of percentage as

Answer: Option D

Explanation:

Let the origianl salary = Rs. 100

It will be 150% of (50% of 100)
= (150/100) * (50/100) * 100 = 75

So New salary is 75, It means his loss is 25%

Answer: Option D

Explanation:

It means that 0.08% of x = 2
$$\begin{aligned} => ( \frac{8}{100 \times 100} \times x) = 2 \\ => x = \frac{2 \times 100 \times 100}{8} \\ => x = 2500 \end{aligned}$$

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

Answer: Option C

Explanation:

Error = (81.5 - 81.472) = 0.028
Required percentage = $$\begin{aligned} \frac{0.028}{81.472} \times 100 = 0.034 % \end{aligned}$$

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