IB Mathematics Analysis and Approaches Question Type 6: Finding Sum of First n Terms Given the Values of Other Sums Exercises

Find the sum of the first 6 terms.

The sum of the first 9 terms of an arithmetic sequence is 81 and the sum of the first 12 terms is 132. Find the sum of the first 15 terms.

Given the sum of the first 4 terms is 14 and the sum of the first 7 terms is 35 for an arithmetic sequence, find the sum of the first 10 terms.

The sum of the first 5 terms of an arithmetic sequence is 35 and the sum of the first 9 terms is 99. Find the sum of the first 7 terms.

Given that $S_8=96$ and $S_3=21$ for an arithmetic sequence, find $S_6$.

For an arithmetic sequence, the sum of the first 7 terms is 56 and the sum of the first 3 terms is 18. Find the sum of the first 5 terms.

Find the sum of the first 8 terms.

Find $S_4$. [6 marks]

Given the sum of the first 8 terms is 40 and the sum of the first 14 terms is 91 for an arithmetic sequence, find the sum of the first 20 terms.