<PRE><B>Question 703164</B>
Eric drove from town A to town B.
 After traveling 1/3 of the journey at an average speed of 75 km/hr, he continued to travel another 300 km to reach town b.
 If the average speed for the whole journey was 90 km/hr, find his average speed for the last 2/3 of the journey?
:
From the given information, 2/3 = 300 km, therefore 1/3 = 150 km
Total distance = 450 km
:
Write a time equation, time = dist/speed
:
let s = the average speed for 2/3 of the journey
:
:1/3 time + 2/3 time = total time
{{{150/75}}} + {{{300/s}}} = {{{450/90}}}
reduce the fractions
2 + {{{300/s}}} = 5
{{{300/s}}} = 5 - 2
{{{300/s}}} = 3
3s = 300
s = 100 km/hr for 2/3 the journey
:
:
Check this using the time equation
{{{150/75}}} + {{{300/100}}} = {{{450/90}}}</PRE>