When working with problems involving equations, you can determine solutions by substituting a known value into the equation and then using mathematical operations to calculate a result.
Matt is driving 63 miles per hour on a long road trip. The equation d = 63t can be used to calculate d, the distance Matt drove in t hours. Find the distance that Matt drives in 4 hours.
Write the equation with 4 substituted for t.
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d = 63(4)
What is the distance that Matt drove?
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Matt drove 252 miles in 4 hours.
Three friends are eating dinner together at a restaurant. They are trying to figure out t, the amount of tip to leave for a meal that costs c dollars. To calculate the tip, they are using the equation t = 0.15c. Their dinners cost $11.90, $10.95, and $10.45. How much of a tip should they leave?
What was c, the total cost of their meals?
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The total cost of their meals was $33.30.
Write the equation with the total cost of their meals substituted for c.
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t = 0.15(33.30)
How much should they leave as a tip?
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t = 4.995
They should leave $5.00 as a tip.
An electrician charges a set fee of $50 plus $35 per hour for repairs. Using the equation
c = 50 + 35t, what will be the total cost, c, of a repair that takes 6 hours to complete?
Write the equation for the cost with 6 substituted for t.
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c = 50 + 35(6)
How much will the repair cost?
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c = 50 + 210
c = 260
The repair will cost $260.