Physics
posted by K on .
A car travels in a straight line with an average velocity of 80 km/hr for 2.5 hours and then with an average velocity of 40 km/hr for 1.5 hours.
a. Calculate the largest displacement for the 4hour trip.
b. Calculate the largest average velocity for the total trip in kilometers per hour.
Please if possible show all work, thanks for you help :)

80*2.5 + 40*1.5 = 200+60 = 260
What does it mean to say "largest average velocity for the total trip"?
There is only one average velocity for the total trip: 260/4 = 65 km/hr
I think they want you to say 80 km/hr, since after the first section the average velocity is lower. However, we know nothing about the velocity at other times. Maybe at some point in the first 2.5 hours the velocity was 300 km/hr, raising the average to 120 km/hr, but then slowed way down so at the end of the 2.5 hours, the average was only 80. Or, maybe at some point in the later section, again the velocity spiked way up, raising the average until then to some large amount.
If the question was posed as you typed it, it was very poorly worded.