## 228. Math Puzzle $5 / 84$

Frank covers the first $300 \mathrm{~m}$ on his way to school in 4 minutes, then takes 4 minutes for $50 \mathrm{~m}$ of stairs, and manages the remaining $600 \mathrm{~m}$ in 10 minutes.

What is his average speed in $\mathrm{km} / \mathrm{h}$?
| Ways | Times |
| :--- | ---: |
| $300 \mathrm{~m}$ | $4 \mathrm{~min}$ |
| $50 \mathrm{~m}$ (Stairs) | $5 \mathrm{~min}$ |
| $600 \mathrm{~m}$ | $10 \mathrm{~min}$ |
| $950 \mathrm{~m}$ | $19 \mathrm{~min}$ |

Speed $=\frac{\text { Distance }}{\text { Time }}=\frac{950}{19}=50 \frac{\mathrm{m}}{\min }=3 \mathrm{~km} / \mathrm{h}$