15.

Suppose an investment of $6,600 doubles in value every 8 years. How much is the investment worth after 40 years?

$528,000

$66,000

$211,200

$105,600

1 answer

To figure out how much the investment is worth after 40 years, we need to determine how many times the investment doubles within that period.

Given:
- Initial investment = $6,600
- Investment doubles every 8 years
- Time period = 40 years

First, we calculate the number of doubling periods in 40 years:
\[ \text{Number of doubling periods} = \frac{40 \, \text{years}}{8 \, \text{years/double}} = 5 \, \text{doubling periods} \]

Now, we calculate the investment value after each doubling period:
\[ \text{Value after 1 doubling period} = 2 \times 6,600 = 13,200 \]
\[ \text{Value after 2 doubling periods} = 2 \times 13,200 = 26,400 \]
\[ \text{Value after 3 doubling periods} = 2 \times 26,400 = 52,800 \]
\[ \text{Value after 4 doubling periods} = 2 \times 52,800 = 105,600 \]
\[ \text{Value after 5 doubling periods} = 2 \times 105,600 = 211,200 \]

So, the investment is worth $211,200 after 40 years.

The correct answer is:
\[ \boxed{211,200} \]