Question

During the first part of a​ trip, a canoeist covered 90 km at a certain speed. He then traveled 42 km at a speed that was 4 ​km/h slower. If the total time for the trip was 8 ​hr, what was the speed on each part of the​ trip?

Answer 1

Answer:

13.467 km/h speed for 48 km distance

13.467-4=9.467 km/h for distance of 42 km

Explanation:

distance covered = 90 km

distance traveled 42 km at the speed of  4 km/h slower

total time = 8 hr

assume speed of first distance be 'x'

speed of 42 km distance will be 'x-4'

time = $\dfrac{distance}{speed}$

$\dfrac{42}{x-4}+\dfrac{48}{x} = 8$

45 x - 96 = 4( x²-4 x)

4 x² - 61 x +96 = 0

$x=\dfrac{61\pm \sqrt{61^2-4(4)(96)} }{2\times 4}$

x = 13.467  ,  1.783

hence we will adopt 13.467 km/h speed for 48 km distance

and 13.467-4=9.467 km/h for distance of 42 km