josh80 wrote:Circular gears P & Q start rotating at the same time at constant speeds. Gear P makes 10 revs/minute and gear Q makes 40 revs/minute. How many seconds after the gears start rotating will gear Q have made exactly 6 more revs than gear P?
6
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10
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15
When elements compete, SUBTRACT THEIR RATES.
Every minute Q makes 40 revolutions and P makes 10 revolutions.
The difference between their rates is 40-10 = 30.
Thus, every minute Q makes 30 more revolutions than P.
To determine how many seconds it will take Q to make 6 more revolutions than P, set up a proportion:
30 revolutions/60 seconds = 6 revolutions/x seconds
30x = 360
x = 12.
The correct answer is
D.
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