You discover an antique in your attic that you purchased at an estate sale 10 years ago for $400. You auction it on Ebay and receive $8,000 for your item. What annual rate of return did you earn

I earned an annual rate of return of 34.9%.

Explanation:

A = P (1 + r) ^n

A is the amount the antique was auctioned = $8000

P is the amount the antique was bought = $400

r is the annual rate of return

n is the duration of the investment = 10 years

$8000 = $400 (1 + r) ^10

(1 + r) ^10 = $8000/$400

(1 + r) ^10 = 20

1 + r = 20^0.1

1 + r = 1.349

r = 1.349 - 1

r = 0.349 * 100 = 34.9%