Find the Degrees of the Rotating Restaurant

A restaurant occupying the top floor of a skyscraper rotates as diners enjoy the view.  Ling and Sarah notice that they began their meal at 7:00 P.M. looking due north.  At 7:45 P.M. they had rotated 180° to a view that was due south.  At this rate, how many degrees will the restaurant rotate in 1 hour?
A.)  90°
B.)  180°
C.)  240°
D.)  270°
E.)  400°

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Set up a proportion.  

The restaurant rotated 180° in 45 minutes.  You need to find how many degrees it would rotate in 60 minutes.

    180°                        x°
--------------    =    --------------   {set up a proportion}
45 minutes          60 minutes

10,800 = 45x   {cross-multiplied}
x = 240   {divided each side by 45}

C.)  240°

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