Question

Emily takes a trip, driving with a constant velocity of $90$ $km/h$ to the north except for a $30$ min rest stop. If Emily's average velocity is $75$ $km/h$ to the north, what is the total distance travelled? (in km)

• A. $124$
  
• B. $225$
  
• C. $150$
  
• D. $280$
  

Answer 1

The correct option is B $225$

Let distance travelled is $x$ km and total journy time is $t$. Emily takes rest of 30min= $\frac{1}{2}$ hours so actual travel time ($t-\frac{1}{2})$ hours,

Using $s=ut$ $\Rightarrow x=90(t-\frac{1}{2})$ ......1

$\to x=75t$ .....2\Equating equations 1 and 2 $\Rightarrow t=3$ hours,

Put the value of $t$ in equation 2, $\Rightarrow x=225$ km