Question 457889
You need 2 equations: 1 for going
and 1 for the return trip
going:
{{{ d = r*t }}}
(1){{{ 144 = r*t }}}
returning:
(2) {{{ 144 = 2r*(t - 4) }}}
From (1):
{{{ t = 144/r }}}
Substitute this into (2)
(2) {{{ 144 = 2r*(144/r - 4) }}}
(2) {{{ 144 = 288 - 8r }}}
(2) {{{ 8r = 144 }}}
(2) {{{ r = 18 }}}
The speed going was 18 mi/hr
check answer:
(1){{{ 144 = 18*t }}}
(1){{{ t = 8 }}}
and
(2) {{{ 144 = 2*18*(8 - 4) }}}
(2) {{{ 144 = 36*4 }}}
(2) {{{ 144 = 144 }}}
OK