A paper pulp company has discovered their cost and revenue functions for each day: C(x) = 2x2 - 250x + 525 and R(x) = -3x2 + 750x + 125, where x is the amount of pulp in tons. If they want to make a profit, what is the range of pulp in tons per day that they should produce? Round to the nearest tenth of a ton which would generate profit.

The correct answer is 49.

Explanation:
This can be represented as an arithmetic sequence, since we are adding the same number each time to find the next number. The general rule for an arithmetic sequence is
,
where a₁ is the first term and d is the common difference.

In this problem, a₁=5, since he starts at 5, and d=4, since he is adding 4 planks per day; this gives us


Letting 12 be n for the 12th day, we have
5+4(12-1)=5+4(11)=5+44=49.