Shatabdi Express without its rake can go$36 \mathrm{km}$ in an hour, and the speed is diminished by a quantity that varies as the square root of the number of wagons attached. If it is known that with four wagons its speed is$24 k\mathrm{m}/\mathrm{h}$, the greatest number of wagons with which the engine can just move is

Read the following and answer the questions that follow. Sahir runs in a triathlon consisting of three phases in the following manner. Running $12 \mathrm{km}$, cycling $24 \mathrm{km}$ and swimming$5 \mathrm{km}$. His speeds in the three phases are in the ratio $2:6:1$. He completes the race in $n$ minutes. Later, he changes his strategy so that the distances he covers in each phase are constant but his speeds are now in the ratio $3:8:1$. The end result is that he completes the race taking $20$ minutes more than the earlier speed. It is also known that he has not changed his running speed when he changes his strategy.

What is his initial speed while swimming?

Read the following and answer the questions that follow. Sahir runs in a triathlon consisting of three phases in the following manner. Running $12 \mathrm{km}$, cycling $24 \mathrm{km}$ and swimming$5 \mathrm{km}$. His speeds in the three phases are in the ratio $2:6:1$. He completes the race in n minutes. Later, he changes his strategy so that the distances he covers in each phase are constant but his speeds are now in the ratio $3:8:1$. The end result is that he completes the race taking $20$ minutes more than the earlier speed. It is also known that he has not changed his running speed when he changes his strategy.