Re: Circular gears P and Q start rotating at the same time at constant spe
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24 Jul 2022, 16:33
Note that we are given revolutions per minute and asked about revolutions in seconds. So we should transform per minute to per second.
Gear P makes 10 revolutions per minute --> gear P makes 10/60 revolutions per second;
Gear Q makes 40 revolutions per minute --> gear Q makes 40/60 revolutions per second.
Let \(t\) be the time in seconds needed for Q to make exactly 6 more revolutions than gear P --> \(\frac{10}{60}t+6=\frac{40}{60}t\) --> \(t=12\).
Answer: D.