$A$ boy started from his house by bicycle at $10:00\, a.m.$ at a speed of $12\, km/hr$. His elder brother started after $1\, hr\, 15\, mins$ by scooter along the same path and caught him at $1:30\, p.m.$ The speed of the scooter will be (in $km/hr$):

$A$ man with $\frac{3}{5}$ of his usual speed reaches the destination $2 \frac{1}{2}$ hours late. Find his usual time to reach the destination? (in $hours$)

$A$ train $50\, m$ long passes a platform $100\, m$ long in $10\, s$. The speed of the train in $m/s$ is:

$A$ train,when moving at an average speed of $40 \, km/hr$,reaches its destination on time. When its average speed becomes $35 \, km/hr$,it reaches its destination $15 \, minutes$ late. Find the length of the journey in $km$.

One aeroplane started $30 \, \text{minutes}$ later than the scheduled time from a place $1500 \, \text{km}$ away from its destination. To reach the destination at the scheduled time,the pilot had to increase the speed by $250 \, \text{km/hr}$. What was the original speed of the aeroplane? (in $\text{km/hr}$)

$A$ starts from a place $P$ to go to a place $Q$. At the same time $B$ starts from $Q$ to $P$. If after meeting each other $A$ and $B$ took $16$ and $25$ $hours$ more respectively to reach their destinations,the ratio of their speeds is