Here, the equation for the slope comes out to be (5t+3)/(2t+1). Greg has taken two cases for t=1 and 100. However, as the value of t increases the slope gets closer to 2.5. Also if we calculate the limit of this function at infinity, it comes out to be 2.5. So can we say that there comes a point where Quantity A will be equal to Quantity B, which will then push the answer to D.
Honestly, there’s no need to consider calculus here. But since you’ve touched on the subject here, let me clarify. You’re saying that as we keep increasing value of t, value of the slope approaches 2.5. The limit of the function (as t tends to infinity) is equal to 2.5? Yes! But does that mean the value of function is = 2.5? No. Its infinitesimally close, but not equal to 2.5.
Remember, its not a quant test : its a quantitative reasoning test. Keep your fundamentals clear and use reasoning skills.