Question

Find sum of given arithmetic progression :
{4+7+ 10 + ....... + 94}
1) 31
2) 30
3) 1519
4) 1470​

Answer 1

a+(n-1)d

94=4+(n-1)3

94=4+3n-3

94-7=3n

29+1

30

Answer 2

Answer:

3) 1519

Step-by-step explanation:

Here,

First term: a=4

Common difference: d=3

Last term: l=94

By formula of A.P, we find the term associated with last term.

tn= a+(n-1)d

94= 4+(n-1)3

90= 3(n-1)

n-1= 30

n=31

Now, sum of terms,

Sn= n/2 (a+l)

Sn= 31/2 (4+94)

Sn= 31*49

Sn= 1519

Cheers!