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When their child was born, her parents invested $40,000 in a plan guaranteed to increase by 3% per year. The logarithmic function y=77.9 log x/40,000  can be used to determine the number of years, y, it takes for the investment to be worth x dollars.

 

After how many years will the investment be worth approximately 100% more than it was originally and how old will their child be when the investment is worth about $400,000?

 

A.) The investment is worth approximately 100% more after 23 years, and the investment is worth $400,000 when their child is about 78 years old 
B.) The investment is  worth approximately 100% more after 8 years, and the investment is worth $40,000 when their child is about 30 years old

C.) The investment is worth approximately 100% more after 30 years, and the investment is worth $400,000 when their child is aboit 50 years old

 Feb 7, 2016
 #1
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(y=77.9 log( x/40,000)

years= 77.9 log (80000/40000)   results in y=23.45 years     "A"

 Feb 7, 2016
 #2
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When their child was born, her parents invested $40,000 in a plan guaranteed to increase by 3% per year. The logarithmic function y=77.9 log x/40,000  can be used to determine the number of years, y, it takes for the investment to be worth x dollars.

 

After how many years will the investment be worth approximately 100% more than it was originally and how old will their child be when the investment is worth about $400,000?

 

A.) The investment is worth approximately 100% more after 23 years, and the investment is worth $400,000 when their child is about 78 years old 
B.) The investment is  worth approximately 100% more after 8 years, and the investment is worth $40,000 when their child is about 30 years old

C.) The investment is worth approximately 100% more after 30 years, and the investment is worth $400,000 when their child is aboit 50 years old

 

ANSWER

 

It will take 23.45 years for the $40,000 to double to $80,000 @ 3% annual comp. interest

It will take 77.90 years fpr the $40,000 to grow to to $400,000@3%,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

From these calculations that the answer is "A"

 Feb 7, 2016

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