Question 344537
Rate*Time=Distance
.
.
.
{{{R*t=D}}}
{{{t=D/R}}}
{{{t[1]=90/120=3/4}}}hr
{{{t[2]=40/90=4/9}}}hr
Total time for the trip was,
{{{T=t[1]+t[2]=3/4+4/9}}}
{{{T=27/36+16/36}}}
{{{T=43/36}}}hr
Total distance for the trip was,
{{{D[t]=90+40}}}
{{{D[t]=130}}}km
So, the average speed was,
{{{V[ave]=D[t]/T=130/(43/36)=(130*36)/43}}}
{{{V[ave]=4680/43}}}kph
or approximately
{{{V[ave]=109}}}kph