SOLUTION: Alphonse starts at point A and runs at a constant rate towards point C. At the same time, Brigitte starts at point B and runs towards point C also at a constant rate. They arrive a
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Question 205967: Alphonse starts at point A and runs at a constant rate towards point C. At the same time, Brigitte starts at point B and runs towards point C also at a constant rate. They arrive at C at exactly thesame moment. If they continue running in the
same directions, Alphonse arrives at B exactly 10 seconds before Brigitte arrives at A. How fast was Brigitte running?
You can put this solution on YOUR website! Alphonse starts at point A and runs at a constant rate towards point C.
At the same time, Brigitte starts at point B and runs towards point C also
at a constant rate.
They arrive at C at exactly the same moment.
If they continue running in the same directions, Alphonse arrives at B
exactly 10 seconds before Brigitte arrives at A.
How fast was Brigitte running?
A|----60m------|C---40m----|B
:
Let a = Al's speed (in meters/sec)
Let b = Brig's speed
:
They arrive at C at the same time equation, =
cross multiply
40a = 60b
a =
a = 1.5b
:
Time for each running 100 meters equation
B's time = A's time + 10 sec = + 10
:
Replace a with 1.5b = + 10
:
Multiply equation by 3 to get rid of the denominators, results
3(100) = 2(100) + 1.5b(10)
:
300 = 200 + 15b
:
300 - 200 = 15b
:
100 = 15b
b =
b = 6 meters/sec is Brig's speed (that's 24 km/hr)
:
:
Check solution
Find A's speed: 1.5*6.667 ~ 10 meters/sec
Find the times
60/10 = 6 sec
40/6.667 ~ 6 sec
