Answer:
The speed of the motor still water​ is 8.33 km per hour.
Step-by-step explanation:
- Let y be the speed of stream be = [tex]5[/tex] km per hour
- Speed of boat in still water be = [tex]x[/tex] km per hour
- Speed of boat down stream be = [tex](x + 5)[/tex] km per hour
- Distance covered = [tex]2 \times 30[/tex] = [tex]60[/tex] km
- Time = 4 hours and 30 minutes = 4.5 hours
Using the formula
               [tex]Time=\frac{Distance}{speed}[/tex]
                  [tex]4.5=\frac{60}{\left(x+y\right)}[/tex]
                [tex]x+y=\frac{60}{4.5}[/tex]
                [tex]x+5=\frac{60}{4.5}[/tex]
             [tex]x+5-5=\frac{60}{4.5}-5[/tex]
                    [tex]x=8.33[/tex]  km per hour
Therefore, the speed of the motor still water​ is 8.33 km per hour.
Keywords: speed, time, distance
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