Advanced MathHardExponential decay after three periods
Advanced Math practice question
A car's value decreases by 10% each year. If the car is worth $800 now, what will it be worth, in dollars, in 3 years?
Answer: 583.2 or 583.20
Each year multiplies by 0.9: 800 × 0.9³ = 800 × 0.729 = 583.2.
Common wrong answers
- If you answered 560
- 560 subtracts 10% of 800 three times (linear decrease); each 10% is taken of the current value.
- If you answered 648
- 648 is the value after TWO years (800 × 0.81).
- If you answered 720
- 720 is after ONE year.
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