Answer
Find out the how much is the investment worth after 40 years .
To prove
As given
Suppose an investment of $6,600 doubles in value every 8 years.
Thus
$6600 is the intial investment.
$6600 doubles i.e becomes $13200 in 8 years.
$13200 doubles i.e becomes $26400 in 16 years.
$26400 doubles i.e becomes $52800 in 24 years.
$52800 doubles i.e becomes $105600 in 32 years.
$105600 doubles i.e becomes $211200 in 40 years.
Therefore the is $211200 is the investment worth after 40 years.
