1) When a student weighing 45 kgs left a class, the average weight of the remaining 59 students increased by 200g. What is the average weight of the remaining 59 stude
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Ans. C
Explanation :
Let the average weight of the 59 students be A.
So the total weight of the 59 of them will be 59*A.
The questions states that when the weight of this student who left is added, the total weight of the class = 59A + 45
When this student is also included, the average weight decreases by 0.2 kgs
\begin{aligned}
\frac{59A + 45}{60} = A - 0.2
\end{aligned}
=> 59A + 45 = 60A - 12
=> 45 + 12 = 60A - 59A
=> A = 57
2) Average of all prime numbers between 30 to
- 1) 37
- 2) 37.8
- 3) 39
- 4) 39.8
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Ans. 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}
3) Reeya obtained 65, 67, 76, 82 and 85 out of 100 in different subjects, What will be the averag
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Ans. B
Explanation :
\begin{aligned}
( \frac {65+67+76+82+85}{5} ) = 75
\end{aligned}
4) Find the sum of first 30 natural numbe
- 1) 470
- 2) 468
- 3) 465
- 4) 463
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Ans. 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}
5) Find the average of first 10 multiples of
- 1) 35.5
- 2) 37.5
- 3) 38.5
- 4) 40.5
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Ans. 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}
6) The average of four consecutive odd numbers is 24. Find the largest numbe
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Ans. 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
7) Average of 10 numbers is zero. At most how many numbers may be greater than ze
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8) Find the average of all numbers between 6 and 34 which are divisible by
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Ans. B
Explanation :
\begin{aligned}
Average = (\frac{10+15+20+25+30}{5}) = \frac{100}{5} =20
\end{aligned}
9) Average of 10 matches is 32, How many runs one should should score to increase his average by 4 ru
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Ans. B
Explanation :
Average after 11 innings should be 36
So, Required score = (11 * 36) - (10 * 32)
= 396 - 320 = 76
10) 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
- 1) 54.48
- 2) 54.68
- 3) 54.60
- 4) 54.58
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Ans. B
Explanation :
\begin{aligned}
\frac{(55 \times 50) +(60 \times 55) +(45 \times 60) }{55 + 60 + 45}
\end{aligned}
\begin{aligned}
\frac{8750}{160} = 54.68
\end{aligned}