SOLUTION: Given the sequence 3;6;9;.....;60. a)Determine the number of terms in the sequence b)Determine the sum of the terms in the sequence

Question 1110215: Given the sequence 3;6;9;.....;60.
a)Determine the number of terms in the sequence
b)Determine the sum of the terms in the sequence
Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!

a) The numbers are the first 20 multiples of 3; so the number of terms in the sequence is 20.

More formally...
difference between first and last terms
divide by common difference to find the number of terms AFTER THE FIRST TERM
you need to count the first term also

b) Since this is an arithmetic sequence (common difference between successive terms), the average of all the numbers is the average of the first and last.

Since in ANY set of numbers the sum is equal to the average multiplied by the number of numbers, the sum of the terms in this sequence is

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