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What is the sum of the arithmetic sequence 3, 9, 15..., if there are 36 terms? a. 3,468 b. 3,888 c. 4,234 d. 4,572
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1 vote
What is the sum of the arithmetic sequence 3, 9, 15..., if there are 36 terms?

a. 3,468
b. 3,888
c. 4,234
d. 4,572

User Marcus Erronius
by
7.6k points

2 Answers

1 vote

Answer:B✓

Explanation:

The answer is 3,888

User Bluetoft
by
7.9k points
3 votes
we know that
the formula of the the sum of the arithmetic sequence is
Sum=n*(a1+an)/2

n=36
a1=3
a36=?

find a36
an=a1+(n-1)*d

for n=2 a2=9
9=3+(2-1)*d----> 9=3+d----> d=6
so
for n=36
a36=a1+(36-1)*6----> a36=3+35*6----> a36=213

Sum=n*(a1+an)/2-----> 36*[3+213]/2----> 3888

the answer is
3888
User Pragnesh Vaghela
by
8.5k points
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