Question 721115
Let {{{ t }}} = the time for both
Let {{{ p }}} = the speed of the plane
{{{ p - 90 }}} = the speed of the car
Equation for car:
(1) {{{ 240 = ( p-90 )*t }}}
Equation for plane:
(2) {{{ 600 = p*t }}}
----------------
(2) {{{ t = 600/p }}}
and
(1) {{{ 240 = ( p - 90 )*( 600/p) }}}
(1) {{{ 240 = 600 - 54000/p }}}
(1) {{{ 240p = 600p - 54000 }}}
(1) {{{ 360p = 54000 }}}
(1) {{{ p = 150 }}}
The plane's speed is 150 mi/hr
check:
(2) {{{ 600 = p*t }}}
(2) {{{ t = 600/150 }}}
(2) {{{ t = 4 }}} hrs
and
(1) {{{ 240 = ( p-90 )*t }}}
(1) {{{ 240 = ( 150-90 )*t }}}
(1) {{{ 240 = 60t }}}
(1) {{{ t = 4 }}} hrs
OK