GeminiHeat wrote:
Alex and Brenda both stand at point X. Alex begins to walk away from Brenda in a straight line at a rate of 4 miles per hour. One hour later, Brenda begins to ride a bicycle in a straight line in the opposite direction at a rate of R miles per hour. If R > 8, which of the following represents the amount of time, in terms of R, that Alex will have been walking when Brenda has covered twice as much distance as Alex?
A. R-4
B. R/(R+4)
C. R/(R-8)
D. 8/(R-8)
E. 2R - 4
Good Question!
After \(1\) hour;
X(Brenda) |----------4----------(Alex)
Let \(R = 10\)
(Brenda)------------------------X---------4------|--------(Alex)
Distance travelled by Brenda at \(10\) mph in time \(t\)= \(10t\)
Distance travelled by Alex at \(4\) mph in time \((t+1)\)= \(4 + 4t\)
We are given;
\(10t = 2(4 + 4t)\)
\(t = 4\)
Therefore, Alex must have travelled for \(5\) hours
Let's check the options;
A. R-4\(10 - 4 = 6\)
B. R/(R+4)\(\frac{10}{(10+4)} = \frac{5}{7}\)
C. R/(R-8)\(\frac{10}{(10-8)} = 5\)
D. 8/(R-8)\(\frac{8}{(10-8)} = 4\)
E. 2R - 4 \(2(10) - 4 = 16\)
Hence, option C