SOLUTION: On a trip of 800 km , Charlie drove at two different speeds. \in one province he drove at 100 km/h and in another at 110 km/h. If the entire trip took seven and one-half hours, the

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Question 180667: On a trip of 800 km , Charlie drove at two different speeds. \in one province he drove at 100 km/h and in another at 110 km/h. If the entire trip took seven and one-half hours, the distance travelled at the 110 km/h speed is?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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On a trip of 800 km , Charlie drove at two different speeds.
\in one province he drove at 100 km/h and in another at 110 km/h.
If the entire trip took seven and one-half hours, the distance traveled at the 110 km/h speed is?
;
Let d = distance traveled at 110 km/hr
then
(800-d) = distance traveled at 100 km/hr
;
Write time equation: Time = dist/speed
;
hrs at 110 + hrs at 100 = 71%2F2 hrs
d%2F110 + %28%28800-d%29%29%2F100 = 7.5
:
Multiply equation by 1100 to get rid of the denominators
1100*d%2F110 + 1100*%28%28800-d%29%29%2F100 = 1100(7.5)
Results
10d + 11(800-d) = 8250
:
10d + 8800 - 11d = 8250
:
10d - 11d = 8250 - 8800
:
-d = -550
:
d = 550 km at 110 km/hr
;
:
Check solution by finding the actual times at each speed (800-550 = 250)
550/110 = 5 hrs
250/100 = 2.5 hrs
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total hrs 7.5