andre drove part of a 260km trip at 80kph and the rest at 100kph. find the distance he traveled at 80kph if his total driving time was 2h 30min

Answer 1

let the distance traveled at the slower speed be x km
distance at faster speed = 260-x

time at slower = x/80
time at faster =(260-x)/100

x/80 + (260-x)/100 = 2.5

multiply by 400
5x + 4(260-x) = 1000
5x + 1050 - 4x = 1000
x = -50

not possible, no solution

(should be obvious from the start,
even if he had gone the entire trip at the faster speed of 100 km/h, it would take him 260/100 hrs or 2.6 hrs)