Reeya obtained 65, 67, 76, 82 and 85 out of 100 in different subjects, What will be the average.

Answer: Option D

Explanation:

Let the average after 17th match is x
then the average before 17th match is x-3

so 16(x-3) + 87 = 17x
=> x = 87 - 48 = 39

Answer: Option B

Explanation:

Average speed will be

$$\begin{aligned} \frac{2xy}{x+y} km/hr = \frac{2(50)(30)}{50+30} km/hr \end{aligned}$$

= 37.5 km/hr

Answer: Option D

Explanation:

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

Answer: Option D

Explanation:

As number of girls and boys is not given so result cant be computed

Answer: Option C

Explanation:

Sum of n natural numbers
$$\begin{aligned} = \frac{n(n+1)}{2} \end{aligned}$$

$$\begin{aligned} = \frac{30(30+1)}{2} = \frac{30(31)}{2} = 465 \end{aligned}$$