MathRevolution wrote:
When 1+2+..........+n=n(n+1)/2, what is the sum of all the positive multiples of 6 to 714, inclusively?
A. 3*119*120 B. 6*119*120 C. 3*118*119 D. 6*120*121 E. 3*120*121
*A solution will be posted in two days.
Half the challenge might be wading through answers as formatted.
For sums of multiples of sequences, I do not use factoring or n(n-1)/2.
I used the general formula for summing[multiples of] an arithmetic sequence, then found the value that matched my answer.
Formula for sum
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