Advertisements
Advertisements
प्रश्न
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.
Advertisements
उत्तर
Given, sum of first n natural numbers = `1/2n^2 + 1/2n`
Sum of natural numbers from 11 to 30
= Sum of first 30 natural numbers – Sum of first 10 natural numbers
= `[1/2(30)^2 + 1/2(30)] - [1/2(10)^2 + 1/2(10)]`
= `900/2 + 30/2 - 100/2 - 10/2` ...[Divide each term by 2]
= 450 + 15 – 50 – 5
= 410
APPEARS IN
संबंधित प्रश्न
Write down the following in the product form: x2y4
The sum of three consecutive odd numbers is 21. Find the numbers.
Reena is 6 years older than her brother Ajay. If the sum of their ages is 28 years, what are their present ages?
Deepak is twice as old as his brother Vikas. If the difference between their ages is 11 years, find their present ages.
Mrs. Goel is 27 years older than her daughter Rekha. After 8 years she will be twice as old as Rekha. Find their present ages.
A man is 4 times as old as his son. After 16 years he will be only twice as old as his son. Find their present ages.
The perimeter of the triangle shown in the following figure is ______.
If I spend f rupees from 100 rupees, the money left with me is ______ rupees.
If m is a whole number, then 2 m denotes a multiple of 2.
The side of an equilateral triangle is shown by l. Express the perimeter of the equilateral triangle using l.
The side length of the top of square table is x. The expression for perimeter is ______.
The speed of car is 55 km/hrs. The distance covered in y hours is ______.
The sum of the multiplication table of natural number ‘n’ is given by 55 × n. Find the sum of table of 10.
The sum of the multiplication table of natural number ‘n’ is given by 55 × n. Find the sum of table of 19.
