Sally's Trip: Find Total D., Avg. Speed in km

[licia589]

sally travels by car from one city to another. she drives for 35.1 min at 94.9 km/h, 12.8 min at 117 km/h, and 53.9 min at 53.7 km/h and she spends 20.6 min eating lunch and buying gas

a)find the total distance traveled. answer in units of km
b) find the average speed for the trip answer in units of km!

please help I've tried figuring this out and none of my answers are right! thanks

 

[himanshu121]

So what u have done so far Welcome to PF and do
READ

https://www.physicsforums.com/showthread.php?s=&threadid=28

 

[Jimmy]

I think licia is waiting for someone to post the answer.

 

[licia589]

no not at all I am just waiting for someone to show me how to do it.. not to give me the answer because the way i have been doing it hasnt been working so please help

 

[Raven]

Licia

Why don't you explain how you've been doing it? Everyone can then point out where you've gone wrong and help you find the right path.

 

[HallsofIvy]

You know exactly how long she was driving at each speed so you can calculate how far she went. For example, she drove 94.9 km/h for 35.1 min (which is 35.1/60= .585 hours) and so went (94.9)(.585)= 55.52 km. Calculate the distance at each speed and add to find the total distance. Add all the times together to find the total time (don't forget the time eating lunch and getting gas) and divide "distance by time" to find the average speed.