Question 885639
Distance  = rate x time
or
{{{ d = r*t }}}
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You are given:
{{{ d = 50 }}} m
{{{ r = 45 }}} km/hr
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First, you have to convert 
meters to km
In terms of just units:
( m ) * ( km/m ) = km
{{{ 50*( 1/1000 ) = .05 }}} m
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Now units are compatible
{{{ d = r*t }}}
 km = ( km/hr) x hrs 
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{{{ .05 = 45t }}}
{{{ t = .05/45 }}}
{{{ t = 1/900 }}} hrs
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Convert hrs to min
{{{ ( 1/900 )*60 = 4/60 }}}
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Convert min to sec
{{{ ( 4/60 )*60 = 4 }}}
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It takes 4 sec to travel 50 m at 45 km/hr