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Example

Solving a Word Problem for the Past Cost of a Car

Apply the seven-step problem-solving strategy to a real-world word problem that asks to find an unknown past value based on a known present value and a related comparative phrase.

Problem: According to the National Automobile Dealers Association, the average cost of a car in 20142014 was $28{,}400. This was $1{,}600 less than six times the cost in 19751975. What was the average cost of a car in 19751975?

  1. Read the problem carefully. The goal is to find a past cost using a present cost.

  2. Identify what to find: the average cost of a car in 19751975.

  3. Name the unknown: Let cc = the average cost of a car in 19751975. The phrase "$1{,}600 less than six times the cost in 19751975" tells us that the cost in 20142014 can be expressed as 6c1,6006c - 1{,}600.

  4. Translate into an equation: The average cost in 20142014 was $28{,}400, so: 6c1,600=28,4006c - 1{,}600 = 28{,}400

  5. Solve the equation. Combine the two operations by first adding 1{,}600 to both sides: 6c=30,0006c = 30{,}000 Divide both sides by 66: c=5,000c = 5{,}000

  6. Check: Is $1{,}600 less than six times $5{,}000 equal to $28{,}400? 6(5{,}000) - 1{,}600 stackrel{?}{=} 28{,}400 30{,}000 - 1{,}600 stackrel{?}{=} 28{,}400 28{,}400 = 28{,}400 checkmark

  7. Answer: The average cost of a car in 19751975 was $5{,}000.

This problem highlights translating comparative language into an equation. The expression 6c1,6006c - 1{,}600 accurately captures the relationship, which directly translates into a two-step equation.

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Updated 2026-06-03

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