Question Detail

Average of all prime numbers between 30 to 50

37
37.8
39
39.8

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
$\begin{aligned} (\frac{31+37+41+43+47}{5}) = \frac{199}{5} = 39.8 \end{aligned}$

1. Find the average of all numbers between 6 and 34 which are divisible by 5

Answer: Option B

Explanation:

$\begin{aligned} Average = (\frac{10+15+20+25+30}{5}) = \frac{100}{5} =20 \end{aligned}$

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

Answer: Option B

Explanation:

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

3. Find the average of first 10 multiples of 7

35.5
37.5
38.5
40.5

Answer: Option C

Explanation:

$\begin{aligned} = \frac {7(1+2+3+...+10)}{10} \end{aligned}$

$\begin{aligned} = \frac {7(10(10+1))}{10 \times 2} \end{aligned}$

$\begin{aligned} = \frac {7(110)}{10 \times 2} = 38.5 \end{aligned}$

4. A library has an average of 510 visitors on Sundays and 240 on other day. The average number of visitors in a month of 30 days starting with sunday is

Answer: Option B

Explanation:

As the month begin with sunday, so there will be five sundays in the month. So result will be:
$\begin{aligned} = (\frac{510 \times 5 + 240 \times 25}{30}) = (\frac{8550}{30}) = 285 \end{aligned}$