### Brain Teasers

# The Fan

Joe Bob just installed a fan system to cool off from the summer heat. The fan spins at a maximum speed of 40 mph and is controlled by a 360 degree turning knob. Assuming the fan is spinning at 15 mph, how much would the knob have to be turned in order to go at a constant speed of 25 mph?

### Answer

90 degrees.You want to increase the speed by 10 mph, which is 1/4 of the total scale (10 mph divided by 40 mph). To do this you need to adjust the knob 1/4 of its total range.

1/4 of 360 degrees is 90 degrees.

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