If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 60, then the average marks of all the students is

Answer: Option B

Explanation:

$$\begin{aligned} ( \frac {65+67+76+82+85}{5} ) = 75 \end{aligned}$$

Answer: Option B

Explanation:

Average after 11 innings should be 36

So, Required score = (11 * 36) - (10 * 32)
= 396 - 320 = 76

Answer: Option D

Explanation:

Prime numbers between 30 and 50 are:
31, 37, 41, 43, 47

Average of prime numbers between 30 to 50 will be
$$\begin{aligned} (\frac{31+37+41+43+47}{5}) = \frac{199}{5} = 39.8 \end{aligned}$$

Answer: Option A

Explanation:

Sum of the present ages of husband, wife and child = (27 * 3 + 3 * 3) years = 90 years.

Sum of the present ages of wife and child = (20 * 2 + 5 * 2) years = 50 years.

Husband's present age = (90 - 50) years = 40 years

Answer: Option D

Explanation:

Suppose total number of students are = X
$$\begin{aligned} Total increase = x*\frac{1}{2} = \frac{x}{2} \\ => \frac{x}{2} = 83-63 = 20 \\ => x = 40 \end{aligned}$$