| this is way out of sync but I want to say how I solved a problem xiggi posted earlier in the thread. It took longer than 10 seconds, but at least it makes sense to me.
BTW, love the thread! keep on the discussion!
A girl rides her bicycle to school at an average speed of 8 mph. She returns to her house using the same route at an average speed of 12 mph. If the round trip took 1 hour, how many miles is the round trip.
A. 8
B. 9 3/5
C. 10
D. 11 1/5
E. 12
ok. so she travels at 8 mi/hr on a path and 12 mi/hr back along the same path.
so label the distance of the path x and the round trip 2x. Traveling 12 mi/hr she went a distance of x mi. and traveling 8 mi /hr she also went a distance of x mi.
if you divide the distance traveled by the speed, you will get how much time it took to travel that distance.
so for her 8 mi/hr trip:
x / ( 8mi/hr) = hrs taken
and for 12 mi/hr trip:
x / (12 mi/hr) = hrs taken.
since the entire trip took 1 hour and only includes the 8 mi/hr trip and the 12 mi/hr trip, you get the equation:
( x/ (8 mi/hr) ) + ( x/ (12 mi/hr) = 1
finding the common denominator:
(3x / (24 mi/hr) ) + (2x / 24 mi/hr ) =1
and adding the fractions:
(5x/ (24 mi/hr ) ) =1
and multiplying by the reciprocal:
x = 24 /5
since you are looking for 2x (roundabout trip) you find:
2x = 48/5
and that equals 9 3/5
sorry bout that. was that lucid? |