I3.3 Two cyclists, initially $(b+26) \mathrm{km}$ apart travelling towards each other with speeds $40 \mathrm{~km} / \mathrm{h}$ and $60 \mathrm{~km} / \mathrm{h}$ respectively. A fly flies back and forth between their noses at $100 \mathrm{~km} / \mathrm{h}$. If the fly flied $c \mathrm{~km}$ before crushed between the cyclists, find $c$.
The velocity of one cyclist relative to the other cyclist is $(40+60) \mathrm{km} / \mathrm{h}=100 \mathrm{~km} / \mathrm{h}$. Distance between the two cyclists $=(24+26) \mathrm{km}=50 \mathrm{~km}$
Time for the two cyclists meet $=\frac{50}{100} \mathrm{~h}=\frac{1}{2} \mathrm{~h}$
The distance the fly flied $=\frac{1}{2} \times 100 \mathrm{~km}=50 \mathrm{~km}$ $\Rightarrow c=50$