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B. Circle B

Step-by-step explanation:

The radius of a circle is the center point of a circle to the outer side of the circle. The diameter of a circle is from one side of the circle to the other in a straight line. We can multiply the radius of circle B by 2 to get the diameter of circle B. The diameter of circle B is 10 and the diameter of circle A is 9, so the larger circle/circumference would be circle B.

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m