Question

Last Sunday, Rachel travelled for 2 hrs at a speed of 40 km/hr and then travelled at 80 km/hr for another 2 hrs. On the very next day, she has travelled for 3 hrs at 40 km/hr and the next journey at a speed of 80 km/hr for 2 hrs. On Tuesday, she could analyze that 60 km/hr was the average speed of her journey on both the days.

• A. True
• B. False

Answer 1

The correct option is B

False

We know that, $Averagespeed=\frac{Totaldistancetravelled}{Totaltimetaken}$

On Sunday, her time of travel for each trip is same i.e 2 hrs.
$\Rightarrow$ $Averagespeed=\frac{(S1+S2)}{2}=\frac{(40+80)}{2}=60km/hr$

Now, on next day, time of travel is different, so we have to find the total distance travelled and total time taken as:

Total distance traveled = $40km/hr\times 3hrs+80km/hr\times 2hrs$

$\Rightarrow$ $120km+160km=280km$

And total time taken = 3 hrs + 2 hrs = 5 hrs

So, $Averagespeed=\frac{280km}{5hrs}=56km/hr$

Since the average speed is different for both the days days. So, given statement is false.