Question Detail

Marks of a student were wrongly entered in computer as 83, actual marks of that student were 63. Due to this mistake average marks of whole class got increased by half (1/2). Find the total number of students in that class.

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}

1. Average of 10 matches is 32, How many runs one should should score to increase his average by 4 runs.

Answer: Option B

Explanation:

Average after 11 innings should be 36

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

2. 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}

3. Average of 10 numbers is zero. At most how many numbers may be greater than zero

Answer: Option D

4. The average score of a cricketer for ten matches is 38.9 runs. If the average for first six matches is 42, then average for last four matches is

33.25
32.25
34.25
34.50

Answer: Option C

Explanation:

\begin{aligned}
= \frac{(38.9 \times 10)-(42 \times 6)}{4}
\end{aligned}

\begin{aligned}
= \frac{(1216 - 750)}{4} = 34.25
\end{aligned}

5. The average of four consecutive odd numbers is 24. Find the largest number.

Answer: Option B

Explanation:

Let the numbers are x, x+2, x+4, x+6, then
\begin{aligned}
=> \frac{x+(x+2)+(x+4)+(x+6)}{4} = 24
\end{aligned}

\begin{aligned}
=> \frac{4x+12)}{4} = 24
\end{aligned}

\begin{aligned}
=> x+3 = 24 => x = 21
\end{aligned}

So largest number is 21 + 6 = 27