Bunuel
Bob, David, and Edward ran a 17.5 miles race. The combined running time of Bob and David exceeded twice Edward's running time by exactly an hour. None of the three ran at a speed exceeding 10 miles per hour. The winner of the race can be
(I) Bob
(II) David
(III) Edward
A. Only II
B. Only I
C. Only I or II
D. Only III
E. I or II or III
We can calculate that everybody took longer than \(\frac{17.5 \text{ miles}}{10 \text{ mi/h}} = 1.75 \text{ hours}\) first.
The relation given is \(t_{Bob} + t_{David} = 2*t_{Edward} + 1\). By plugging in the minimum time, we also know \(t_{Bob} + t_{David} > 4.5\).
Edward could possible be the fastest by splitting the total time between Bob and David equally, hence \(t_{Bob} = t_{David} = \frac{1}{2}(2*t_{Edward} + 1) > t_{Edward} \).
We may also let either Bob or David have a faster time than Edward and let the remaining person take the rest of the time. For example, \(t_{Edward} = 2, t_{Bob} \text{ or } t_{David} = 1.9 \text{, and } t_{David} \text{ or } t_{Bob} = 3.1\).
Then anyone could have been the fastest.
Answer: E