Question 55446: here i am again... plz help m regarding this problem...thanks a lot!!
19.Rose drove her car from her home to the province and back, a total distance of 120km. Her average speed returning was 3kph slower than her average speed going to the province. If her total driving time was 9 hours, what was her average speed in going to the province?
thanks alot tutorz!!
Answer by Edwin McCravy(20056) (Show Source):
You can put this solution on YOUR website! 19.Rose drove her car from her home to the
province and back, a total distance of 120km. Her
average speed returning was 3kph slower than her
average speed going to the province. If her total
driving time was 9 hours, what was her average speed
in going to the province? thanks a lot tutorz!!
Rose drove very slowly to have taken 9 hours to travel
only 120km. I will assume the traffic was extremely
heavy both ways.
The words "a total distance of 120km" are ambiguous. Is
it 60km going and 60km returning for a total of 120km?
Or is the total distance between her home and the province
120km? Either way she is still driving very slowly.
I will assume she is driving the slowest and the distance
between her home and the province is 60km.
Make this chart:
DISTANCE RATE TIME
Going
Returning
Fill in the two distances, which are both 60:
DISTANCE RATE TIME
Going 60
Returning 60
Since the question is
>>...what was her average speed in going to the province...<<
We will let x represent her speed going, so we fill in x for
the rate going:
DISTANCE RATE TIME
Going 60 x
Returning 60
>>...Her average speed returning was 3kph slower...<<
3kph slower than x kph is x-3 kph. So we fill that in for the
rate returning:
DISTANCE RATE TIME
60 x
Returning 60 x-3
Now we use the fact that TIME = DISTANCE/RATE to fill in the
times:
DISTANCE RATE TIME
Going 60 x 60/x
Returning 60 x-3 60/(x-3)
To find the equation we use this:
>>...her total driving time was 9 hours...<<
We add the two TIME's and put that equal to 9
60/x + 60/(x-3) = 9
Can you solve that by first multiplying through by
LCD = x(x-3) ? If not post again.
You will get two answers: x = 16 and x = 4/3
We must discard the 4/3, since that would cause her
rate returning to be negative. So the answer is
a very slow 16 kph.
If we assume it was 120km from her home to the
province the equation is not factorable and the
answer is 28.251 kph, which is still very slow.
Edwin
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