A general physics question

a car travels at a rate of 25km/h for 4 mins,
then 50km/h for 8 mins,
finally 20km/h for 2 mins.
(a) find the total distance traveled in km
(b) average speed for the entire trip in m/s

i need help working this problem

u have to change all km/h to m/s
so 25 * 1000/3600 = 6.95 m/s for 4 * 60 = 240 seconds
50 * 1000/3600 = 13.89 m/s for 8 * 60 = 480 seconds
20 * 1000/3600 = 5.56 m/s for 2 * 60 = 120 seconds

to find the distance u have to multiply every speed with it's time then add them all together like this :

6.95 m/s * 240 s = 1668 m
13.89 m/s * 480 s = 6667.2 m
5.56 m/s * 120 s = 667.2 m

the distance is :

1668 + 6667.2 + 667.2 = 9002.4 m = 9.0024 KM

average speed = total distane/total time =
9002.4/840 = 10.71 m/s almost 11 m/s

this is hard.......there is a simple way v = x/t soo x = v * t and roll on....
good luck ....

welcome..........the trick is just...
when u want to change from km/h to m/s u just have to multiply km/h by 1000/3600 which equals 5/18

when u want to change from m/s to km/h u have to devide m/s by 1000/3600 which equals 5/18

and good luck twice :)

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(a) Σs = v(1)t(1) + v(2)t(2) + v(3)t(3) = 25km/h * (4/60)h + 50km/h * (8/60)h + 20km/h * (2/60)h = 9km
(b) speed in km = total distance / total time used = 9km / ((4+8+2)/60)h = 39km/h
speed in meters = [39km/h / (3.6km/h)]m/s = 11m/s