Question

find the sum of natural numbers from 21 to 80 {arithmetic Progression} class 10​

Answer 1

Answer:

21,22,23_------------80

a=21 d =1 ,an = 80

an = a+(n-1)d

80= 21+(n-1)1

59 = (n-1)

60 = n

s60= 60/2(2*21+(60-1)1

s60= 30(42+59)

s60= 30(101)

s60 = 3030