SOLUTION: The first number in the set of 11 consecutive multiples of 3 is 21. What is the middle number in the set?

Question 1144821: The first number in the set of 11 consecutive multiples of 3 is 21. What is the middle number in the set?
Answer by ikleyn(52794) (Show Source): You can put this solution on YOUR website!
.

The middle number is the 6-th term in this sequence.


 = 21 + (6-1)*3.


Calculate.


I used the standard formula for the n-th term of an arithmetic progression.

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