Question

Find the sum of natural numbers between 20 and 100

Answer 1

num of terms=80
1st term=20
common difference=1
Sn= n/2(2a+(n-1)d)
Sn= 80/2(40+79 . 1)
Sn= 80/2(119)
Sn= 40(119) = 4760

Answer 2

Answer:

The sum of natural numbers between 20 and 100 is 4760.

Step-by-step explanation:

Number of terms = 80

1st term = 20

Common difference = 1 ( that is the difference between any two terms is 1)  

 

Applying the Sum of n numbers formula,  

Sn=n/2[2a+(n-1)d]

Where n=80    (n= number of natural numbers to be calculated)

           a=20    (a= starting number)

           d=1       (Difference between any two numbers)

Sn=80/2[2(20)+79.1]

On equating the above formula, we get

  = 40(119)

  = 4760

Therefore sum of natural numbers between 20 and 100 is 4760