Find the sum of the series 20+27+34+41+...+664+671

Question

unklerhaukus · Answer

20+671=691
27+664=691
can you use this pattern some how

anonymous · Answer

I can't remember how to do this on paper, but I find this would be easier to do with a program.

callisto · Answer

First term = 20
Common difference = 27-20 = 7
no. of terms = (671 - 20)/7 +1 = ???
Them use the formula
Sum = (n/2) (a+l), where a = first term, l= last term and n= no. of terms

lgbasallote · Answer

i would suggest you find the number of terms then use the formula for sum of arithmetic series $$\large S_n = \frac{n(A_1 + A_n)}{2}$$ but unkle's could work

callisto · Answer

To make it clear
no of terms
$$=\frac{ (671 - 20)}{7} +1$$