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

Question : 1

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 : 2

The average of 11 numbers is 63. If the average of first six numbers is 60 and the last six numbers is 65, then the 6th number is

a) 60

b) 64

c) 62

d) 57

Question : 3

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 : 4

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

Question : 5

The average of 15 numbers is 7. If the average of the first 8 numbers is 6.5 and the average of the last 8 numbers is 8.5, then the middle number is :

a) 23

b) 15

c) 13

d) 10

Question : 6

The average temperature of the first 4 days of a week was 37°C and that of the last 4 days of the week was 41°C. If the average temperature of the whole week was 39°C, the temperature of the fourth day was

a) 38.5°C

b) 40°C

c) 39°C

d) 38°C