model 4 find nth average from 1st & last number Section-Wise Topic Notes With Detailed Explanation And Example Questions

Question : 1

Average of n numbers is a. The first number is increased by 2, second one is increased by 4, the third one is increased by 8 and so on. The average of the new numbers is

a) a+2 ${2^{n} – 1}/n$

b) a+${2^{n }- 1}/n$

c) a+$2^{n-1} /n$

d) a+${2^{n-1} – 1}/n$

Question : 2

The average of nine numbers is 50. The average of the first five numbers is 54 and that of the last three numbers is 52. Then the sixth number is

a) 34

b) 44

c) 24

d) 30

Question : 3

The average of 8 numbers is 20. The average of first two numbers is 15$1/2$ and that of the next three is 21$1/3$. If the sixth number be less than the seventh and eighth numbers by 4 and 7 respectively, then the eighth number is :

a) 22

b) 27

c) 25

d) 18

Question : 4

The average of 11 results is 50. If the average of the first six results is 49 and that of the last six is 52, the sixth no. is

a) 50

b) 56

c) 52

d) 48

Question : 5

The average of two numbers is 8 and the average of other three numbers is 3. The average of the five numbers is :

a) 3

b) 6

c) 5

d) 2

Question : 6

In a certain year, the average monthly income of a person was Rs.3,400. For the first eight months of the year, his average monthly income was Rs.3,160 and for the last five months, it was Rs.4,120. His income in the eighth month of the year was

a) Rs.5,080

b) Rs.5,520

c) Rs.15,520

d) Rs.3,160