Question

When their child was born, her parents invested $40,000 in a plan guaranteed to increase by 3% per year. The logarithmic function y equals 77.9 log start fraction x over 40,000 end fraction can be used to determine the number of years, y, it takes for the investment to be worth x dollars.
Exponential graph modeling the equation y equals seventy seven point nine times the log of the quantity x over forty thousand. Graph comes up from the left along the y axis and goes through the point forty thousand comma zero and continues to the right towards infinity.

After how many years will the investment be worth approximately 75% more than it was originally and how old will their child be when the investment is worth about $80,000?

The investment is worth approximately 75% more after 19 years, and the investment is worth $80,000 when their child is about 23 years old.
The investment is worth approximately 75% more after 4 years, and the investment is worth $80,000 when their child is about 25 years old.
The investment is worth approximately 75% more after 14 years, and the investment is worth $80,000 when their child is about 31 years old.
The investment is worth approximately 75% more after 27 years, and the investment is worth $80,000 when their child is about 19 years old.

Answer 1

This website is designed to help those in need. But, if you post way to many questions it's unlikely you'll get help. So please be moderate on how many things you post. And,  lets take it a step at a time.