Question 1114941
Let {{{ t }}} = time in hrs for both the
plane and the car
Let {{{ s }}} = the speed of the plane in mi/hr
{{{ s - 90 }}} = the speed in mi/hr of the car
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Equation for the plane:
(1) {{{ 300 = s*t }}}
Equation for the car:
(2) {{{ 180 = ( s-90 )*t }}}
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(1) {{{ s = 300/t }}}
Plug (1) into (2)
(2) {{{ 180 = ( 300/t - 90 )*t }}}
(2) {{{ 180 = 300 - 90t }}}
(2) {{{ 90t = 120 }}}
(2) {{{ t = 4/3 }}}
and
(1) {{{ s = 300/t }}}
(1) {{{ s = 300/(4/3) }}}
(1) {{{ s = 900/4 }}}
(1) {{{ s = 225 }}}
The speed of the plane is 225 mi/hr
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check:
(1) {{{ 300 = s*t }}}
(1) {{{ 300 = 225*( 4/3 ) }}}
(1) {{{ 3*300 = 4*225 }}}
(1) {{{ 900 = 900 }}}
and
(2) {{{  180 = ( s-90 )*t }}}
(2) {{{ 180 = ( 225 - 90 )*(4/3) }}}
(2) {{{ 180 = 135*(4/3) }}}
(2) {{{ 540 = 540 }}}
OK