169+ Problems on Average With Explanation

Q:

The average marks of a student in 7 subjects is 85. His average marks in 6 subjects except English is 83. What is his marks in English ?

A) 97	B) 98
C) 92	D) 93

Answer & Explanation Answer: A) 97

Explanation:

Marks in English = 85×7 – 83×6

= 595 – 498

= 97

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Q:

What will be the average of the first 7 positive odd numbers divisible by 5?

A) 45	B) 35
C) 40	D) 32

Answer & Explanation Answer: B) 35

Explanation:

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Q:

The mean of 100 observations is 40. It is found that an observation 84 was misread as 48. Then the correct mean is ?

A) 40.36	B) 41.24
C) 41.92	D) 42.05

Answer & Explanation Answer: A) 40.36

Explanation:

Given,

mean of 100 observations is 40

=> Total of 100 observations = 40 x 100 = 4000

84 is misread as 48

=> Difference = 84 - 48 = 36

=> Now, new total of 100 observations = 4000 + 36 = 4036

Correct Mean = 4036/100 = 40.36

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Q:

In a cinema hall for the matinee show which started at 2.30 pm and ended at 5.30 pm the vehicle parking lot had only three wheelers (auto rickshaws) and four wheelers. Today the wheels of the vehicles parked was counted and found to be 240. What could be the number of three wheelers parked therein ?

A) 48	B) 41
C) 45	D) 43

Answer & Explanation Answer: A) 48

Explanation:

3X + 4y = 240
by substitute through options 48 is correct

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Q:

In a mixture of three varities of oils , the ratio of their weight is 4 : 5 : 8. If 5 kg of oils of the first variety, 10 kg of the second variety and some quantity of oils of the third variety are added to the mixture, the ratio of the weights of three varieties of oils becomes as 5 : 7 : 9 in the final mixture, find the quantity of third variety of oil was ?

A) 15 kg	B) 25 kg
C) 35 kg	D) 45 kg

Answer & Explanation Answer: D) 45 kg

Explanation:

Let the ratio of initial quantity of oils be 'x' => 4x, 5x & 8x.
Let k be the quantity of third variety of oil in the final mixture.
Let the ratio of initial quantity of oils be 'y'
From given details,
4x + 5 = 5y ..... (1)
5x + 10 = 7y .....(2)
8x + k = 9y ......(3)

By solving (1) & (2), we get
x = 5 & y = 5

From (3) => k = 5

Therefore, quantity of third variety of oil was 9y = 9(5) = 45kg.

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Q:

The average of marks in 3 subjects is 224. The first subject marks is twice the second and the second subject marks is twice the third. Find the second subject marks ?

A) 384	B) 96
C) 192	D) 206

Answer & Explanation Answer: C) 192

Explanation:

Let the third subject marks be 'x'
=> Second subject marks = 2x
=> Third subject marks = 4x
Given avg = 224
x + 2x + 4x = 224 x 3
=> 7x = 224 x 3
=> x = 96
Hence, Second subject marks = 2x = 2 x 96 = 192.

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Q:

Out of three numbers, the first is twice the second and is half of the third. If the average of the three numbers is 56, what will be the sum of the highest number and the lowest number?

A) 120	B) 160
C) 80	D) 60

Answer & Explanation Answer: A) 120

Explanation:

Let the three numbers be x, y, z.

From the gien data,

x = 2y ....(1)

x = z/2 => z = 2(2y) = 4y .....(From 1) ...........(2)

Given average of three numbers = 56

Then,

$\frac{x + y + z}{3} = 56 \frac{2 y + y + 4 y}{3} = 56 (From 1 & 2) 7 y = 56 x 3 y = 24$

Now,

x = 2y => x = 2 x 24 = 48

z = 4y = 4 x 24 = 96

Now, the highest number is z = 96 & smallest number is y = 24

Hence, required sum of highest number and smallest number

= z + y

= 96 + 24

= 120.

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Q:

Find the average of first 30 multiples of 7.

A) 94.8	B) 99.6
C) 104.4	D) 108.5

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