### Important Formulas and Facts

1) Average = Sum of observations / Number of observations
2) Suppose an object covers a certain distance at 'a' kmph and an equal distance at 'b' kmph. Then the average speed during the whole journey = $\left(\frac{2ab}{a+b}\right)$

1)

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) 3:5

2)

In a school with 600 students, the average age of the, boys is 12 years and that of the girls is 11 years.- If the average age of the school is 11 years 9 months, then the number of girls in the school is :

A) 150

B) 250

C) 350

D) 450

3)

A certain factory employed 600 men and 400 women and the average wage was Rs. 25.50 per day. If a woman got Rs. 5 less than a man, then what are their daily wages ?

A) Man : Rs. 25; Woman : Rs. 20

B) Man • Rs. 27.50, Woman : Rs. 22.50

C) Man : Rs. 30, Woman : Rs. 25

D) Man : Rs. 32.50, Woman : Rs. 27.50

4)

After replacing an old member by a new member, it was found that the average age of five members of a'club is the safrie as it was 3 years ago. What is the difference between the ages of the replaced and the new member ?

A) 2 years

B) 4 years

C) 8 years

D) 15 years

5)

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) 35 years

B) 40 years

C) 50 years

D) None of these

6)

The average age of a husband and his wife was 23 years at the time of their marriage. After five years they have a one-year old child. The average age of the family now is :

A) 19 years

B) 23 years

C) 28.5 years

D) 29.3 years

7)

Of the three numbers, the average of the first and the second is greater than the average of the second and the third by 15. What is the difference between the fire and the third of the three numbers ?

A) 15

B) 45

C) 60

E) None of these

8)

Of the three numbers, the first is twice the second and the second is twice the three. The average of the reciprocal of the numbers is  7/72. The numbers are :

A) 16, 8, 4

B) 20, 10, 5

C) 24, 12, 6

D) 36, 18, 9

9)

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) Rs. 9000

B) Rs. 15000

C) Rs. 18000

D) Rs. 21000

10)

In the first 10 overs of a cricket game, the run rate was only 3.2. What should be the run rate in the remaining 40 overs to reach the target of 282 runs ?

A) 6.25

B) 6.5

C) 6.75

D) 7

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