Rate*Time = Distance
Time = Distance/Rate
The cyclist has an 18 mile headstart. If his staff were traveling at 18 mph, the 18 mile gap would never get smaller. and they'd never catch up with the cyclist. But they are traveling at 45 mph, 45-18=27 mph faster than the cyclist, so they are closing the 18 mile gap at 27 mph:
Time = (18 miles) / (27 mph) = ____________?
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Another way to do it:
The distance the cyclist has traveled in time t is given by the linear equation y = 18t
The equation for the staff is y = 45t - 18 (at t=0, they are 18 miles behind the cyclist, or -18). The staff catches up with the cyclist when they have traveled the same distance:
45t - 18 = 18t
27t = 18
t = ____?

Matt H.
01/26/15