Suppose an investment of $6,200 doubles in value every 13 years l. how much is the investment worth after 78 years

Well, 78 / 13 = 6   So, the investment will double 6 times.

6,200 x 2 = 12,400     12,400 x 2 = 24,800       24,800 x 2 = 59,600

59,600 x 2 = 119,200    119,200 x 2 = 238,400    238,400 x 2 = 476,800

There's your final $476,800!