For the Rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78.

Question

For an 10 month period, the last term is and the series sum is .

For a 15 month period, the last term is and the series sum is .

For a 20 month period, the last term is and the series sum is .

Answer 1

The nth term is n.

The sum of n terms is n(n+1)/2

Answer 2

Can you please show me how to solve. I appreciate it.

Answer 3

a. 55