Question 856040
A motorist travelled from town X to town Y at an average speed of 90 km/h. 
after travelling 1/3 of the journey in 45 min. he continued to travel another 120 km to reach town Y.
 find his average speed for the second part of the journey.
:
Find the total length of the journey (d)
{{{2/3}}}d = 120 km
d = 180 km
:
let s = his speed for last 2/3 of the journey
:
Write a time equation (change 45 min to .75 hrs); time = dist/speed
.75 + {{{120/s}}} = 180/90
{{{120/s}}} = 2 - .75
{{{120/s}}} = 1.25
s = 120/1.25
s = 96 km/hr for the 2nd half of the journey