AVERAGE

Important Formulas:  

1. Sum of first n natural numbers 

 

 2. Sum of the squares of first n natural numbers

 

3. Average of first n positive integers = 

4. Average of first n positive integers =  n+1


5. Average of first n odd integers =  n

Note: 0 is neither odd nor even 




PROBLEMS

1.  Find the sum of first 40 natural numbers

(a)800  (b) 810  (c)820  (d) 840  (e)none of these 

 Ans: (c)

2.  Find the average of first 10 multiples of 7

 (a)37.5  (b) 38.5  (c)39  (d)40  (e)none of these 

Ans: (b)

3. A batsman makes a score of 85 runs in the 16th match and thus increases his average by 2. Find his average after 16th match.

(a)55  (b) 57  (c)60  (d)62   (e)none of these

Ans:(a)

 





4. Average weight of 10 people increased by 1.5 kg when one person of 45 kg is replaced by a new man. Then weight of the new man is

 (a)50  (b) 55  (c)60  (d)65   (e)none of these

Ans: (c)
 
Total weight increased = 1.5*10 = 15
Weight of new person = 45+15 =60