What is the third term in this arithmetic series?

Question

An arithmetic series of 10 terms has a sum of 1100. The second term is twice the first term. What is the third

third term*

Answer 1

if x is the first term then, 2x is the second term.
the common difference is 2x - x = x

the 10th term of the sequence is 10x


Arimethic sum formula:

S = n (a1 + an) / 2

n = number of terms (10)
a1= first term (x)
an = last term (10x)

given the sum is 1100

plug in chunks

1100 = 10 (x + 10x)/2
2200 = 10 (11x)
220 = 11x
x = 20

20, 40, 60, 80, ...,200

so the third term is 60


hope it helps
Rec

Answer 2

series is:

20 40 ----> 60 <--- 80 100 120 140 160 180 200

Answer 3

Sum of first n words is n cases a million/2 the sum of the extremes,i.e., S(n) = n( a million/2) [ T(a million) + T(n) ] = (n/2 ) [ a + { a + ( n-a million ) d } ] = ( n/2 ) ( 2a ) + ( n/2 ) ( n-a million ) d = na + ( a million/2 ) n(n-a million)d.......................Q.E.D.