Advanced MathMediumThree years of 10% decline
Advanced Math practice question
A machine's value falls by 10% each year. If it is worth $900 now, what will it be worth, in dollars, in 3 years?
Answer: 656.1
Each year multiplies the value by 0.9: 900 × 0.9³ = 900 × 0.729 = 656.1.
Common wrong answers
- If you answered 630
- 630 subtracts 10% of the ORIGINAL three times (90 × 3). Each year's 10% is taken of a smaller value.
- If you answered 729
- 729 is 900 × 0.81, only two years of decline.
- If you answered 810
- 810 is the value after one year.
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