Question 89099
s = rate on sides roads
f = rate on freeway
{{{s = 40/t}}} is his rate on side roads. We don't actually know what t is, but
{{{f = 30/t}}} is his rate on the freeways and it's the same t, so the ratio
{{{(40/t) / (30/t) = 4/3}}} is the ratio os his rate on side roads to
his rate on freeways
{{{s/f = 4/3}}}
multiply both siides by {{{f}}}
{{{s = (4/3)*f}}}
Also given is {{{s = f + 7}}}
{{{(4/3)*f = f + 7}}}
{{{4f = 3f + 21}}}
{{{f = 21}}}
{{{s = f + 7}}}
{{{s = 28}}}
Is the ratio true? {{{s/f = 4/3}}}
{{{28/21 = 4/3}}} Yes
So, his rate on the side roads is 28 mph