Question

If the first term in an arithmetic series is 3, the last term is 136, and the sum is 1390, what are the first 3 terms?

Answer 1

first 3 terms are 3,10,17
you add 7
to find this take 136-3 which is 133 and then find what divides 133 so there are no decimals.

Answer 2

but 19 also divides 133, so cant it be add 19? and then it would be 3, 24, 43?

Answer 3

it does, but if you do the math, using 19 as the additive does not sum up the terms to 1390.

Answer 4

to find the sum of an arithmetic series, use the formula \[s_n=(n(a_1+a_n))/2\]

Answer 5

\[s_n\] is your sum, n is the number of terms, \[a_1\] is your first term, and \[a_n\] is your last term

Answer 6

after finding n, then you can use the equation \[a_n=a_1+(n-1)d\]
and solving for d gives you the difference between terms

Answer 7

got it thanks!