Thank you for reporting, we will resolve it shortly
Q.
A train covers the first half of the distance between two stations with a speed of $40\, km/h$ and the other half with $60\, km/h$. Then its average speed is :
Solution:
$v _{ avg }=\frac{2 v _{1} v _{2}}{ v _{1}+ v _{1}}$
$=\frac{2 \times 40 \times 60}{40+60}$
$=48\, km / h$