Question 1078220
Rate * Time = Distance
{{{60*t[1]=D}}}
{{{t[1]=D/60}}}
and
{{{40*t[2]=D}}}
{{{t[2]=D/40}}}
So then the total distance traveled was {{{2D}}} and the total time used was {{{t[1]+t[2]}}} so the average rate is,
{{{R[AVE]=(2D)/(t[1]+t[2])}}}
Substituting,
{{{R[AVE]=(2D)/(D/60+D/40)}}}
.
.
{{{R[AVE]=2/(1/60+1/40)}}}
.
.
{{{R[AVE]=2/(2/120+3/120)}}}
.
.
{{{R[AVE]=2/(5/120)}}}
.
.
{{{R[AVE]=240/5}}}
.
.
Work that out for your final answer.