Question 1029020
Let {{{ t }}} = the time in hrs going from A to B
{{{ t - 1/3 }}} = the time in hrs on return trip
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Equation for A to B
(1) {{{ d = 750t }}}
Equation for B to A
(2) {{{ d = 900*( t - 1/3 ) }}}
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By substitution:
(2) {{{ 750t = 900*( t - 1/3 ) }}}
(2) {{{ 750t = 900t - 300 }}}
(2) {{{ 150t = 300 }}}
(2) {{{ t = 2 }}}
and
{{{ t - 1/3 = 2 - 1/3 }}}
{{{ t - 1/3 = 1 + 2/3 }}}
and
{{{ (2/3)*60 = 40 }}} min
The return time is 1 hr and 40 min
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check:
(1) {{{ d = 750t }}}
(1) {{{ d = 750*2 }}}
(1) {{{ d = 1500 }}} km
and
(2) {{{ d = 900*( 2 - 1/3 ) }}}
(2) {{{ d = 900*(5/3) }}}
(2) {{{ d = 1500 }}} km
OK