SOLUTION: I need help in these two questions I also want the working out steps 1) Normally I drive to work at 60km/h. If I drive at 72km/h I cut 8 minutes off my time for the trip. What

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Question 357289: I need help in these two questions
I also want the working out steps
1) Normally I drive to work at 60km/h. If I drive at 72km/h I cut 8 minutes off my time for the trip. What distance do I travel?
2) My moto boat normally travels at 24km/h in still water. One day I travelled 36 km against a constant current in a river. if i had travelled with the current, I would have travelled 48km in the same time. How fast was the current?
thank you
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
1) Normally I drive to work at 60km/h.
If I drive at 72km/h I cut 8 minutes off my time for the trip.
What distance do I travel?
:
Let d = his travel distance
:
Change min to hrs
:
Write a time equation; time = dist/speed
:
60km time - 8 min = 72km time
- =
Multiply by 720 to get rid of the denominators, results:
12d - 12(8) = 10d
12d - 96 = 10d
12d - 10d = 96
2d = 96
d -
d = 48 km distance traveled
:
:
Check this by finding the actual times
48/60 = .8 hrs
48/72 = .67 hrs
---------------
differ: .13 hrs which is 8 min
:
:
:
2) My motor boat normally travels at 24km/h in still water.
One day I traveled 36 km against a constant current in a river.
if i had travelled with the current, I would have traveled 48km in the same time.
How fast was the current?
:
Let c = the rate of the current
:
Write a time equation, Time = dist/speed
:
Against time = with time
=
Cross multiply
36(24+c) = 48(24-c)
864 + 36c = 1152 - 48c
36c + 48c = 1152 - 864
84c = 288
c =
c = 3.43 km/h is the current
:
:
Confirm this, find the times
= 1.75 hrs
= 1.75 hrs