In this problem, we have the sequence
5,9,13,17,21,...
Is an arithmetic sequence
the common difference is d=4
there are 20 terms (rows) in the sequence
Remember that
The rule to find the sum of the first n terms of the arithmetic sequence is equal to
[tex]S=\frac{n}{2} [2a_1+(n-1)d][/tex]where
n=20
a1=5 ----> first term
d=4
substitute given values
[tex]S=\frac{20}{2}[2(5)+(20-1)4][/tex]S=860
therefore
