169+ Problems on Average With Explanation

Q:

Of the following, which is greater than ½ ?

Indicate ALL such fractions.

A) 2/5	B) 4/7
C) 4/9	D) 5/11

Answer & Explanation Answer: B) 4/7

Explanation:

One way to deal with fractions is to convert them all to decimals.

In this case all you would need to do is to see which is greater than 0.5.

Otherwise to see which is greater than ½, double the numerator and see if the result is greater than the denominator. In B doubling the numerator gives us 8, which is bigger than 7.

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Filed Under: Average - Quantitative Aptitude - Arithmetic Ability
Exam Prep: GRE

12 25620

Q:

The average of six numbers is 3.95. The average of two of them is 3.4, while the average of the other two is 3.85. What is the average of the remaining two numbers ?

A) 3.6	B) 4.6
C) 6.5	D) 7.3

Answer & Explanation Answer: B) 4.6

Explanation:

Sum of the remaining two numbers = (3.95 * 6) - [(3.4 * 2) + (3.85 * 2)]

= 23.70 - (6.8 + 7.7) = 23.70 - 14.5 = 9.20.

Required average = (9.2 / 2) = 4.6.

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37 25602

Q:

In Arun's opinion, his weight is greater than 65 kg but leas than 72 kg. His brother does not agree with Arun and he thinks that Arun's weight is greater than 60 kg but less than 70 kg. His mother's view is that his weight cannot be greater than 68 kg. If all of them are correct in their estimation, what is the average of diferent probable weights of Arun ?

A) 55.5 kg	B) 66.5 kg
C) 77.5 kg	D) 88.5 kg

Answer & Explanation Answer: B) 66.5 kg

Explanation:

Let Arun's weight be X kg.

According to Arun, 65 < X < 72.

According to Arun's brother, 60 < X < 70.

According to Arun's mother, X < 68.

The values satisfying all the above conditions are 66 and 67.

Required average = (66 + 67) / 2 = 66.5 kg

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21 25308

Q:

A family consists of grandparents, parents and three grandchildren. The average age of the grandparents is 67 years, that of the parents is 35 years and that of the grandchildren is 6 years. What is the average age of the family ?

A) 31( 5/7)	B) 32 (6/7)
C) 34(4/7)	D) 35(4/9)

Answer & Explanation Answer: A) 31( 5/7)

Explanation:

Required average = (67 * 2 + 35 * 2 + 6 * 3) / (2 + 2 + 3)

= (134 + 70 + 18) / 7 = 222 / 7 = 31(5/7) years.

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11 24652

Q:

The mean temperature of Monday to Wednesday was 37C and of Tuesday to Thursday was 34C . If the temperature on Thursday was (4/5) th that of Monday, the temperature on Thursday was?

Answer

$\inline \fn_jvn M+T+W =(37\times 3)^{0}=111^{0}C$ -----------(1)

$\inline \fn_jvn T+W+Th=(34\times 3)^{0}=102^{0}C$

$\inline \fn_jvn \Rightarrow T+W+\frac{4}{5}M = 102^{0}C$ --------------(2)

(1) - (2) gives

$\inline \fn_jvn \frac{1}{5}$ th of temperature on Monday = $111^{0}-102^{0}=9^{0}C$

$\inline \fn_jvn \Rightarrow$ Temperature on Monday = $\inline \fn_jvn 45^{0}C$

$\inline \fn_jvn \therefore$ Temperature on Thursday = $\inline \fn_jvn \frac{4}{5}\times 45^{0}=36^{0}$

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Subject: Average - Quantitative Aptitude - Arithmetic Ability

160 24347

Q:

The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years, The ratio of the number of boys to the number of girls in the class is :

A) 1 : 2	B) 2 : 3
C) 3 : 4	D) 4 : 5

Answer & Explanation Answer: B) 2 : 3

Explanation:

Let the ratio be k : 1. Then,

k * 16.4 + 1 * 15.4 = (k + 1) * 15.8

<=> (16.4 - 15.8) k = (15.8 - 15.4) <=> k = 0.4/0.6 = 2/3.

Required ratio = 2/3 : 1 = 2 : 3.

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37 23304

Q:

David obtained 76, 65, 82, 67 and 85 marks (out of 100) in English, Mathematics,Physics, Chemistry and Biology What are his average marks ?

A) 75	B) 68
C) 65	D) 60

Answer & Explanation Answer: A) 75

Explanation:

Average = (76 + 65 + 82 + 67 + 85 )/ 5 = 375/5 = 75.

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24 23112

Q:

If the arithmetic mean of seventy-five numbers is calculated, it is 35. if each number is increased by 5, then mean of new numbers is :

A) 30	B) 40
C) 50	D) 60

Answer & Explanation Answer: B) 40

Explanation:

Let the numbers are $x_{1,} x_{2,} . . . . . . . x_{75}$

By Hypothesis , $\frac{x_{1} + x_{2} + . . . . x_{75}}{75} = 35$ ......(i)

Mean of new numbers = $\frac{(x_{1} + 5) + (x_{2} + 5) + . . . . . . . (x_{75} + 5)}{75}$

$\frac{x_{1} + x_{2} + . . . . . . x_{75} + 5 * 75}{75}$

$\frac{x_{1} + x_{2} + . . . . . . x_{75}}{75} + \frac{375}{75} = 35 + 5 = 40$ By (i)

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43 22234

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