d = vt
a. 48 min = 0.8 h
slower = -
(x - y).0.8 = 6
x-y = 7.5 (i)
b. 36 min = 0.6 h
faster = +
(x+y).0.6 = 6
x+y = 10 (ii)
c. x - y = 7.5
y = x - 7.5
substitute into the second equation (ii)
x + (x-7.5) = 10
2x = 17.5
x = 8.75 km/h
time at usual speed x = 8.75:
[tex]\tt t =\dfrac{6}{8.75}=0.686 h = 41.16\:minute[/tex]
