You can put this solution on YOUR website! A black mamba travels 20 miles per hour for 1/4 mile. How many seconds does it take to travel the 1/4 mile?
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d = r*t
t = d/r = 0.25/20
t = 0.0125 hours
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0.0125 hr * 60 min/hr * 60 sec/min = 45 seconds
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Notice how including the units clarifies it.
