Advertisements
Advertisements
Question
The sum of first n natural numbers is given by `1/2n^2 + 1/2n`. Find the sum of first 11 natural numbers.
Advertisements
Solution
Given, sum of first n natural numbers = `1/2n^2 + 1/2n`
Sum of first 11 natural numbers = `1/2(11)^2 + 1/2(11)` ...[Put n = 11]
= `1/2 xx 121 + 11/2`
= `121/2 + 11/2`
= `132/2`
= 66
APPEARS IN
RELATED QUESTIONS
Write down the following in the product form: 9xy2z
If 9 is added to a certain number, the result is 36. Find the number.
If 11 is subtracted from 4 times a number, the result is 89. Find the number.
The sum of three consecutive natural numbers is 114. Find the numbers.
When Raju multiplies a certain number by 17 and adds 4 to the product, he gets 225. Find that number.
Find two numbers such that one of them exceeds the other by 18 and their sum is 92.
One out of two numbers is thrice the other. If their sum is 124, find the numbers.
Find two numbers such that one of them is five times the other and their difference is 132.
Reena is 6 years older than her brother Ajay. If the sum of their ages is 28 years, what are their present ages?
The perimeter of the triangle shown in the following figure is ______.
The additive inverse of an integer x is 2x.
The side of a regular hexagon is denoted by l. Express the perimeter of the hexagon using l.
(Hint: A regular hexagon has all its six sides equal in length.)
The diameter of a circle is a line which joins two points on the circle and also passed through the centre of the circle. (In the adjoining figure AB is a diameter of the circle; C is its centre.) Express the diameter of the circle (d) in terms of its radius (r).
The side length of the top of square table is x. The expression for perimeter is ______.
Find the perimeter of the figure given below:
The sum of first n natural numbers is given by `1/2n^2 + 1/2n`. Find the sum of first 5 natural numbers.
The sum of first n natural numbers is given by `1/2n^2 + 1/2n`. Find the sum of natural numbers from 11 to 30.
If 
= 2x + 3, 
= `3/2x + 7` and 
= x – 3 then find the value of:
`1/2`
+ 
– 3
