Rajesh covers a certain distance by bus at $16 \text{ km/h}$ and returns to the starting point on a cycle at $9 \text{ km/h}$. His average speed for the whole journey is (in $\text{km/h}$):

$A$ truck covers $224 \ km$ in $4 \ hours$. The average speed of a bike is $\frac{1}{4}$ of the average speed of the truck. How much distance will the bike cover in $7 \ hours$? (in $km$)

$A$ farmer travelled a distance of $61 \, km$ in $9 \, hrs$. He travelled partly on foot at the rate of $4 \, km/hr$ and partly on bicycle at the rate of $9 \, km/hr$. The distance travelled on foot is (in $km$):

$A$ train travelling with a speed of $60 \, km/h$ catches another train travelling in the same direction and then leaves it $120 \, m$ behind in $18 \, seconds$. The speed of the second train is (in $km/h$):

$A$ train leaves a station $A$ at $7:00 \text{ am}$ and reaches another station $B$ at $11:00 \text{ am}.$ Another train leaves station $B$ at $8:00 \text{ am}$ and reaches $A$ at $11:30 \text{ am}.$ At what time do the two trains cross each other?

$A$ train running at a speed of $40 \, m/s$ crosses a pole in $21 \, s$ less than the time it requires to cross a bridge $3.5$ times its length at the same speed. What is the length of the bridge (in $m$)?