169+ Problems on Average With Explanation

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

160 25958

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 24517

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 24380

Q:

The average age of husband, wife and their child 3 years ago was 27 years and that of wife and the child 5 years ago was 20 years. The present age of the husband is

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

Answer & Explanation Answer: B) 40

Explanation:

Sum of the present ages of husband, wife and child = (27 x 3 + 3 x 3) years = 90 years.

Sum of the present ages of wife and child (20 x 2 + 5 x 2) years = 50 years.

Husband's present age = (90 - 50) years = 40 years.

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14 23622

Q:

Find the average of first 30 multiples of 7.

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

Answer & Explanation Answer: D) 108.5

Explanation:

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Exam Prep: Bank Exams

8 23494

Q:

The average price of three items of furniture is Rs. 15000. If their prices are in the ratio 3:5:7, the price of the cheapest item is :

A) 6000	B) 7000
C) 8888	D) 9000

Answer & Explanation Answer: D) 9000

Explanation:

Let their prices be 3x, 5x and 7x.

Then, 3x + 5x + 7x = (15000 * 3) or x = 3000.

Cost of cheapest item = 3x = Rs. 9000.

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26 23400

Q:

The median of the numbers 3, 1, 1 5, 2 and 7 is

A) 3.5	B) 2.5
C) 2	D) 3

Answer & Explanation Answer: B) 2.5

Explanation:

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Exam Prep: Bank Exams

1 23176

Q:

A motorist travels to a place 150 km away at an average speed of 50 km/hr and returns at 30 km/hr. His average speed for the whole journey in km/hr is :

A) 35	B) 36
C) 37.5	D) 38.2

Answer & Explanation Answer: C) 37.5

Explanation:

Average speed = (2xy) /(x + y) km/hr

= (2 * 50 * 30) / (50 + 30) km/hr.

37.5 km/hr.

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