Posted by Kayley on Tuesday, October 6, 2009 at 5:40am.
a car goes at a constant speed for 120 kms, on the way back he goes at half the speed. he drives for a total of 4 hours and 30 minutes. what are the two speeds?

algebra  Reiny, Tuesday, October 6, 2009 at 7:56am
let the speed on the first trip be x km/h
then the speed on the return trip will be x/2 km/h
Time for first part = 120/x hours
and on the return trip = 120/(x/2) = 240/x hours
then 120/x + 240/x = 4.5
360/x = 4.5
x = 360/4.5
= 80
so he went 80 km/h for the first part and only 40 km/h on the way back.
check:
time for first part = 120/80 = 1.5 hrs
on way back = 120/40 = 3 hrs, for a total of 4.5 hrs.
Answer This Question
Related Questions
 maths  A man goes upstream for a distance of 10 kms in 5 hours. Another man ...
 algerbia  a tugboat goes 120 miles up streem in 15 hours it takes 10 hours to ...
 math  Two race cars are speeding around the racetrack at different speeds. One ...
 physics  Two race cars are speeding around the racetrack at different speeds. ...
 math  Consider two toy cars. Car A starts from rest and speeds up with constant...
 Physics  Consider two toy cars. Car A starts from rest and speeds up with ...
 Physics  Consider two toy cars. Car A starts from rest and speeds up with ...
 algebra  A motorvoat goes 36 miles upstream on a river whose current is running...
 Algebra  car a leaves phoenix heading north at a constant speed of 40mph car b ...
 Physics  A car goes North at 55mi/hr for 1.3 hrs. It then goes East at 65mi/hr ...
More Related Questions