Find the sum of the 18th term of the arithmetic sequence 3,5,7,9,11..
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Find the sum of the 18th term of the arithmetic sequence 3,5,7,9,11..
Find the sum of the 18th term of the arithmetic sequence 3,5,7,9,11..
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Answer:
To find the sum of 18th term we have to find the 18th term by using the formula an=a1+(n-1)d
a1=3
d=2
an=a1+(n-1)d
a18=3+(18-1)2
a18=3+(17)2
a18=3+34
a18=37
since we already have the 18th term we can now
find the sum using the formula Sn=n(a1+an) / 2
Sn=n(a1+an) / 2
S18=18(3+37) / 2
S18=18(40) / 2
S18=720 / 2
S18=360