AlgebraHardTwo-variable word problem with a difference
Algebra practice question
A plumber's bill for one job was $780 for 12 hours of skilled work and 8 hours of unskilled work. The skilled rate is $15 per hour more than the unskilled rate. What is the unskilled hourly rate, in dollars?
Answer: 30
Let the unskilled rate be u; the skilled rate is u + 15. Then 12(u + 15) + 8u = 780 → 20u + 180 = 780 → 20u = 600 → u = 30.
Common wrong answers
- If you answered 39
- 39 is 780 ÷ 20, ignoring the $15 difference.
- If you answered 45
- 45 is the skilled rate.
- If you answered 48
- 48 comes from 20u − 180 = 780, subtracting 180 instead of adding.
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