Question 389581
A motorist traveled 115 km on an expressway at an average speed of 92 km/h and
 another 45 minutes on the other roads.
 If the average speed for his whole journey was 80 km/h, how far did he travel on the other road
:
Let d = distance traveled on "other road"
:
Change 45 min to .75 hrs
:
Write a time equation: time = dist/speed
{{{115/92}}} + .75 = {{{((d+115))/80}}}
:
LCM of 92 and 80: multiply by 1840, results:
20(115) + .75(1840) = 23(d + 115)
2300 + 1380 = 23d + 2645
23d = 1035
d = 1035/23
d = 45 km on other road
:
:
Check solution in original equation
{{{115/92}}} + .75 = {{{((45+115))/80}}}
1.25 + .75 = 2