Question

If the mean of first n natural number is 15, then n =
(a)15
(b)30
(c)14
(d)29

Answer 1

SOLUTION :  

The correct option is (d) : 29

Given : MEAN of First n odd natural numbers is 15

First n natural numbers are : 1,2,3.........n  

MEAN = Sum of all the observations/ Total number of observations

MEAN = (1 + 2 + 3 + ……+ n )/n

MEAN = (n/2 (n + 1)) / n  

[The sum of the first n natural numbers : Sn = n/2 (a + l ) = n/2(1 + n) = n/2(n +1)]

15  = (n + 1) /2  

15 × 2 = n + 1

30 = n + 1

n = 30 - 1

n = 29

Hence, the value of n is 29 .  

HOPE THIS ANSWER WILL HELP YOU……

Answer 2

Answer:

Step-by-step explanation:

Answer :-

Correct option is (d) 29.

Given :-

Mean of first n natural number is 15

To Find :-

Value of n.

Formula to be used :-

Mean = Sum of all the observations/ Total number of observations

Mean = (1 + 2 + 3 + ……+ n )/n

Mean = (n/2 (n + 1)) / n  

Solution :-

Putting all the values, we get

Mean = (n/2 (n + 1)) / n  

⇒  15  = (n + 1) /2  

⇒  n + 1 = 30

⇒  n = 30 - 1  

⇒  n = 29

Hence, the value of n is 29.