    Directions: Study the following questions carefully and answer the questions given below.
Important for :
1
The average annual income (in Rs.) of certain agricultural workers is P and that of other workers is Q . The number of agricultural workers is 9 times that of other workers. Then the average monthly income (in Rs.) of all the workers is :
» Explain it
D
Let the number of other workers be x.

Then, number of agricultural workers = 9x.

Total number of workers = 9x + x = 10x.

So, Average monthaly income

 = P x (9x) + Q x (x) = x[9P + Q ] 10x 10x

 = (9P + Q) 10

2
A family consist of grandparents, parents and two grandchildren. The average age of the grandparents is 56 years, that of the parents is 27 years and that of the grandchildren is 7 years. What is the average of the family?
» Explain it
C
First, we find out the normal ages of candidates:

Grand parents(2 candidates) = 56 x 2

Parents (2 candidates) = 27 x 2

Two grandchildren = 7 x 2.

The total candidates are 6. then,

 Average = 56 x 2 + 27 x 2 + 7 x 2 ⇒ 112 + 54 + 14 2 + 2 + 2 6

 = 180 = 30 years 6

3
A library has an average of 430 visitors on Sundays and 270 on other days. The around average of the number of visitors per day in a month of 31 days beginning with a Saturday is:
» Explain it
D

Since the month begins with a saturady , So there will be five sundays in the month,

 Req. Avg. = 430 x 5 + 270 x 26 ⇒ 2150 + 7020 31 31

 ⇒ 9170 =   295.80 ≈ 296. 31

So, the arround value of vistiors per day is 296.

4
If the average marks of three batches of 40, 50 and 60 students respectively is  30, 50 and 70, then the average marks of all the students is:
» Explain it
B
 Req Avg = 40 x 30 + 50 x 50 + 60 x 70 30 + 50+ 70

 ⇒ 1200 + 2500 + 4200 150

 ⇒ 7900 = 52.66 150

Hence, option (B) is correct.

5
The average weight of 18 boys in a class is 45.55 kgs and that of the remaining 4 boys is 35.25 kgs. Find the average weight of all the boys in the class.
» Explain it
C
 Reqd Avg = 18 x 45.55 + 4 x 35.25 ⇒ 819.9 + 141 18 + 4 22

 ⇒ 960.9 =   43.67 kgs 22

Hence, option (C) is correct.