Please help!

[kaseo]

There are two cars each car travels a distance of 120km. Car 1 arrives 40min earlier and travels 9km/hr faster than the slower car. What is the speed of the fast car in km/hr?
Thanks!

 

[lev888]

There are two cars each car travels a distance of 120km. Car 1 arrives 40min earlier and travels 9km/hr faster than the slower car. What is the speed of the fast car in km/hr?
Thanks!

Where are you stuck? Do you know the relevant formulas?
Please read posting guidelines.

 

[kaseo]

Where are you stuck? Do you know the relevant formulas?
Please read posting guidelines.

Hi,
Sorry new to forum. I tried the following...substituted v1 and t1...expanded and then tried to solve for v...but got stuck
?1=?2+9 and ?1=?2−40t
?=120=?1?1=?2?2

 

[Dr.Peterson]

Hi,
Sorry new to forum. I tried the following...substituted v1 and t1...expanded and then tried to solve for v...but got stuck
?1=?2+9 and ?1=?2−40t
?=120=?1?1=?2?2

I don't think you meant to say 40t, since you haven't defined t. The time difference is just 40 minutes.

But you need consistent units in the equations. If speeds are in km/h, then times need to be in hours, not minutes. That's probably your main error.

If you still have trouble, please show your actual work solving the equations, so we can see where you get stuck.

 

[HallsofIvy]

Hi,
Sorry new to forum. I tried the following...substituted v1 and t1...expanded and then tried to solve for v...but got stuck
?1=?2+9 and ?1=?2−40t
?=120=?1?1=?2?2

If I were your teacher I would object to you using "v1" and "v2" and "t1" and "t2" without first saying what they meant. You should say something like "Let v1 be the speed, in km/hr, of the faster car, v2 the speed, in km/hr of the slower car, t1 the time, in hours, it takes the faster car to go 120 km and t2 the time, in hours, it takes the slower car to go 120 km".

Then you can write v1= v2+ 9, t1= t2- 2/3, v1t1= 120, and v2t2= 120.

Notice that in "t1= t2- 2/3" the time is 40 minutes so 40/60= 2/3 hour and t1 and t2 are in hours.

 

[Deleted member 4993]

There are two cars each car travels a distance of 120km. Car 1 arrives 40min earlier and travels 9km/hr faster than the slower car. What is the speed of the fast car in km/hr?
Thanks!

Hi,
Sorry new to forum. I tried the following...substituted v1 and t1...expanded and then tried to solve for v...but got stuck
?1=?2+9 and ?1=?2−40t
?=120=?1?1=?2?2

With the above mentioned (response #5) corrections - please share your complete work (the expansion) .