What is the sum of all the even numbers from 20 to 70

the even numbers starting from 20 to 70 when being add form an A.P

the first term being 20 the last term 70 and common difference = 2

Let us first find the number of terms in it

suppose 70 is the nth term .

nth term of A.P= a+ ( n-1) d here a= 20 and d = 2

70 = 20 +( n-1) * 2

70-20 = (n-1)*2

50= (n-1)*2

50/2 = n-1

25 = n-1

25 +1 = n

26 = n

let us now find sum of these 26 terms

sum formula for n terms = n ( 2a+ ( n-1) d)

2

26 ( 2* 20 + ( 26-1)* 2)

2

13 ( 40 + 25 * 2)

13 ( 40 +50 )

13 ( 90 )

1170 Answer.

22,24,26,28,32,34,36,38,40,42,44,46,48,52,54,56,58,60,62,64,66,68

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