Average Set I

1. Average of the first 5 natural numbers is?
a. 5
b. 4
c. 3

d. 2

Sum of first 5 natural numbers= (1+2+3+4+5)= 15
Average of first 5 natural numbers= 15/5= 3

2. What is the average of all odd numbers upto 100?

Sum of all odd numbers till 100 is 2500(i.e. 50 numbers)
Average= 2500/50=50

3. 36a + 36b = 576. What is the average of a & b?

36a + 36b = 576
36( a+b ) = 576
a+b = 576/36
= 16
Average of a & b = (sum of a & b )/ 2
= 16 / 2
= 8

4. The average of 11, 23 & x is 40. What is value of x ?

average of 11, 23 & x = 40
(11 + 23 + x) / 3 = 40
34 + x = 40 *3
x = 120 – 34
= 86

5. What is the average of first 10 multiples of 3?

average of first 10 multiples of 3=165/10
=16.5

6. What is the average of the following numbers?
42    34    56    58   60

average of numbers is 250/5
=50

7. If the average of 25 student’s age is 17. If we include the age of the teacher the average increase by 1. What is the age of the teacher?

Consider x= 25, y=17 yr z=18 yr
Age of the teacher= 18+25(18-17)= 43 yr

8. What is the average of the first 49 natural numbers?

average of natural number is  n(n+1)/2*n = (n+1)/2
= (49+1)/2= 25

also see

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