What is the sum of the arithmetic series where n=100 , t1=7 and t2=205

Answer 1

if t1 = 7 and t2 = 205
then d = 205-7 = 198

sum(100) = (100/2)(2(7) + 99(198))
= 50(19616)
= 980800

Answer 2

So we know n=100, t1=7, t100=205,
We will use this formula to find the sum Sn=(n/2)(a1+tn) (There are many formulas to find the sum)
S100=(100/2)(7+205)
=10,600 the answer is 10,600.