thinkblue wrote:
The safety distance \(D\) (meters) between cars moving on a motorway depends on their speed \(V\) (meters per second):
\(D = \frac{V^2}{100} + 9\)
If two cars want to maintain a time interval of 1 second between each other, which of the following speeds will breach the safety regulation?
(C) 2008 GMAT Club - m09#31
* 5 m/s
* 10 m/s
* 25 m/s
* 50 m/s
* 90 m/s
Actual Distance = Velocity x 1 second
(1) \(D = \frac{5^2}{100} + 9 \hspace{10} \Rightarrow Distance_{safe} \hspace{5} = \hspace{5} 9.25 \hspace{5} > \hspace{5} Distance_{actual} \hspace{3}(5 m)\)
BREACH(2) \(D = \frac{10^2}{100} + 9 \hspace{10} \Rightarrow Distance_{safe} \hspace{5} = \hspace{5} 10 \hspace{5} = \hspace{5} Distance_{actual} \hspace{3}(10 m)\)
On Par, FINE(3) \(D = \frac{25^2}{100} + 9 \hspace{10} \Rightarrow Distance_{safe} \hspace{5} = \hspace{5} 15.25 \hspace{5} < \hspace{5} Distance_{actual} \hspace{3}(25 m)\)
FINE(4) \(D = \frac{50^2}{100} + 9 \hspace{10} \Rightarrow Distance_{safe} \hspace{5} = \hspace{5} 34 \hspace{5} < \hspace{5} Distance_{actual} \hspace{3}(34 m)\)
FINE(5) \(D = \frac{90^2}{100} + 9 \hspace{10} \Rightarrow Distance_{safe} \hspace{5} = \hspace{5} 90 \hspace{5} = \hspace{5} Distance_{actual} \hspace{3}(90 m)\)
On Par, FINEClearly, first choice of 5 m/s speed violates the regulation because distance maintained (5 m) is less than what the rule suggests.
Answer A.
I think you got confused which distance should be greater than the other.