1. The problem statement, all variables and given/known data With an initial deposit of $100, the balance in a bank account after t years is f(t)=100(108)t dollars. Find the average ROC over the intervals of [0, 0.5] and [0, 1] 2. Relevant equations It first describes in the book the manner in which you solve this problem as such: Δf= f(x1)-f(x0), Δx=x1-x0 So you calculate the first one, then divide it by the calculated result of the second one In the book, it gives this example. --Compute the avg ROC of v with respect to T over the interval [273,300]. Δv/Δt = (20√300 - 20√273)/(300-273) ≈ 15.95/27 ≈ 0.59 m/s per K 3. The attempt at a solution So, I had already solved a problem for avg ROC using that formula and it was correct. Now, given that the answer to my current problem is in the back of the book, I cannot seem to match it. My attempt for the ordered pair [0, 0.5] is as follows: f(t) = 100(108)0.5-100(108)0 Any number to the power of zero = 1, therefore: 100(108)0.5-100(1) 1,039.230485 - 100 = 939.2304845 This would be the upper half, then divide this by the lower half, or x1-x0 which is 0.5 - 0...so 939.2304845 / 0.5 = 1,879.460969. The book gives the answer as 7.8461 for just that ordered pair. Once I figure out where I went wrong, I can figure out the second ordered pair. Appreciate any help. EDIT: Wow I feel stupid. Ok, well, it is 1.08, not 108. Fixing that, and I get the right answer. Carry on, nothing to see here.