Find Sn for each arithmetic series.

a1= 62, d = 12, n = 7

Formula is Sn = n/2(a1 + an)

Don't know what the d stands for or how to use it in the formula.

Answer is 686.

Question

Find Sn for each arithmetic series.

a1= 62, d = 12, n = 7

Formula is Sn = n/2(a1 + an)

Don't know what the d stands for or how to use it in the formula.

Answer is 686.

callisto · Answer

a7 = a1 + (n-1)(d) = 62 + (7-1)(12) = 134
Sn = (7/2) (62 + 134) =?

kropot72 · Answer

d stands for the common difference between consecutive terms of the progression.
In this case the first term is 62 and the second term is 62 +12 = 74

callisto · Answer

n is the number of term while an is the last term. In this case, the last term is a7

callisto · Answer

you need d to find the last term
an = a1 + (n-1) d