Question 179315
ok, lets call the distance d, the rate r, and the time t
:
d=40t.....trip to
d=60t.....trip back
:
solve for t
:
t=d/40....trip to
t=d/60....trip back
:
now lets take the time traveled for the entire to and back trip and multiply it by average rate for the whole trip which will be equal to 2d
:
{{{((d/40)+(d/60))R=2d}}}
:
{{{((3d/120)+(2d/120))R=2d}}}found common denominator on left
:
{{{((3+2)/120)R=2}}}divided all terms by d
:
{{{5R=240}}}combined numerator on left and multiplied by 120 on both sides
:
{{{highlight(R=48)}}}mph average for whole trip
: