Question 336969
Rate*Time=Distance
{{{R*t=D}}}
t1 is the time while the car moves at 94 kph.
{{{94*t1=D}}}
{{{t1=D/94}}} 
The units are in hours, let's convert to minutes.
{{{t1=(60/94)D=(30/47)D}}}
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t2 is the time at rest.
{{{t2=21}}}
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Average speed is total distance divided by total time.
{{{D/(t1+t2)=84.9/60=849/600=283/200}}}
{{{D/((30/47)D+21)=283/200}}}
{{{200D=283((30/47)D+21)}}}
Multiply both side by {{{47}}}
{{{47(200D)=283(30D+47*21)}}}
{{{9400D=8490D+279321}}}
{{{9210D=279321}}}
{{{D=306.95}}}km
Then from above,
{{{t1=(30/47)(306.95)=195.9}}} minutes
{{{t=t1+t2=195.9+21=216.9}}} minutes
{{{t=3.61}}} hrs
{{{t}}}={{{3}}} hrs {{{37}}} minutes.