Question 1053620
Let {{{ s }}} = the average speed of the car in km/hr
Let {{{ t }}} = the time in hrs the car takes to get to town B
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How far did the bus get in the 1st 45 min?
{{{ d[1] = 60*(3/4) }}}
{{{ d[1] = 45 }}} km
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Start a stop watch when the car leaves town A
Let {{{ t }}} = time in hrs on stop watch when car
gets to town B
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Equation for the car:
(1) {{{ 140 = s*t }}}
Equation for the bus:
(2) {{{ 140 - 45 = 60*( t + 1/4 ) }}}
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(2) {{{ 95 = 60t + 15 }}}
(2) {{{ 60t = 80 }}}
(2) {{{ t = 4/3 }}}
and
(1) {{{ 140 = s*t }}}
(1) {{{ 140 = s*(4/3) }}}
(1) {{{ s = (3/4)*140 }}}
(1) {{{ s = 105 }}}
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The average speed of the car is 105 km/hr
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check answer:
The total time for the bus is:
{{{ 3/4 + ( 4/3 + 1/4 ) }}}
{{{ 9/12 + 16/12 + 3/12 = 28/12 }}}
{{{ 28/12 = 7/3 }}}
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The bus travels {{{ 140 }}} km for {{{ 7/3 }}} hrs
{{{ 140 = 60*(7/3) }}}
{{{ 420 = 60*7 }}}
{{{ 420 = 420 }}}
OK