A $1,000 investment takes a 10% loss each year. What will be the value 3 years?

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A $1,000 investment takes a 10% loss each year. What will be the value 3 years?

10% is 0.1. Our Balance function B(y) where y is the number of years since the start is:
B(y) = 1000(1 - 0.1)^y
B(y) = 1000(0.9)^y

We want to know B(3):
B(3) = 1000(0.9)^3
B(3) = 1000(0.729)
B(3) = 729