Kai wrote the number 85 on the board. Is 85 prime or composite? Explain
1 answer:
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Answer:
390
Step-by-step explanation:
The formula of sum of arithmetic sequence is
The number of this series are 2, 4, 6, 8, 10, 12, . . . . , 60.
The first term ( a ) = 2
The 30th even number is 60
The Tn is the term of the sequence
So the equation is
30/2 x ( 2 + )
= 60
30/2 x ( 2 + 60 )
30/2 x (62)
1860/2
390