a)

1 km = 1000 m

1 h = 60 min

 

$6\frac{\text{km}}{\text{h}}=6\cdot \frac{1000\text{m}}{\text{h}}=\underline{6000\frac{\text{m}}{\text{h}}}=6000\cdot \frac{\text{min}}{60\text{min}}=\underline{100\frac{\text{m}}{\text{min}}}$  

 

$\underline{30\frac{\text{km}}{\text{h}}}=30000\frac{\text{m}}{\text{h}}=30000\cdot \frac{\text{m}}{60\text{min}}=\underline{500\frac{\text{m}}{\text{min}}}$  

 

$950\frac{\text{m}}{\text{min}}=950\frac{\text{m}}{\frac{1}{60}\text{h}}=950\cdot 60\frac{\text{m}}{\text{h}}=\underline{57000\frac{\text{m}}{\text{h}}}=\underline{57\frac{\text{km}}{\text{h}}}$            

 

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b)

$100\frac{\text{km}}{\text{h}}=100\cdot \frac{1000\text{m}}{\text{h}}=\underline{100000\frac{\text{m}}{\text{h}}}=100000\frac{\text{m}}{60\text{min}}\approx \underline{1666,67\frac{\text{m}}{\text{min}}}$   

 

$\underline{80\frac{\text{km}}{\text{h}}}=80000\frac{\text{m}}{\text{h}}=80000\cdot \frac{\text{m}}{60\text{min}}\approx 1333,33\frac{\text{m}}{\text{min}}$   

 

 

$250,5\frac{\text{m}}{\text{min}}=250,5\cdot \frac{\text{m}}{\frac{1}{60}\text{h}}=250,5\cdot 60\frac{\text{m}}{\text{h}}=\underline{15030\frac{\text{m}}{\text{h}}}=\underline{15,03\frac{\text{km}}{\text{h}}}$