Data Sufficiency

Hi,

can someone try this and let me know your answer. this question is from OG-12 . DS no 87.

Is the number of seconds required to travel d1 feet at
r1 feet per second greater than the number of seconds
required to travel d2 feet at r2 feet per second?
(1) d1 is 30 greater than d2.
(2) r1 is 30 greater than r2.

I don't agree with the answer given in the OG.
Answer is given in OG as E But i think it is C.

My explanationtion

questions asks Is d1/r1 > d2/r2

1. using the condition 1 , we cannot determine since r1 and r2 are still unknown.
2. Using the condition 2 , we cannot determine since d1 and d1 are still unknown.

using both , it becomes

d2+30/r2+30 > d2/r2.
From this we can infer that first fraction is greater than second fraction.
becase whenever we add same number to numerator and denominator , the value of fraction increases..

So using both the statements we can determine the value which is YES to the question asked and answer should be C.
Please share your explanation.