SOLUTION: Determine the number of terms in the arithmetic series: a1=10 an=74 sn=378

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Question 742502: Determine the number of terms in the arithmetic series:
a1=10
an=74
sn=378
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
sum%28ai%2Ci=1%2Cn%29=%28n%2F2%29%28a%5B1%5D%2Ba%5Bn%5D%29

given: a%5B1%5D=10,a%5Bn%5D=74, and sum%28ai%2Ci=1%2Cn%29=378
378=%28n%2F2%29%2810%2B74%29
378=%28n%2F2%29%2884%29
378=42n
378%2F42=n
9=n