Question

sarah work at a concession stand for 2 hours and erans 22.50$, but if she works for 4 hours she earns $45. what is the rate of change

Answer 1

$15.50/(2 h) = $7.75/h = $31.00/(4 h)

Sarah makes $7.75 per hour.

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While you might be interested in hours per dollar, the customary way to express earnings is in dollars per hour. Either is a "rate of change."