SOLUTION: Javier wants to invest $6000 in a savings account. Determine the interest rate (simple interest) required for Javier 's investment to double in value in 14 years. Round your answer

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Question 1111067: Javier wants to invest $6000 in a savings account. Determine the interest rate (simple interest) required for Javier 's investment to double in value in 14 years. Round your answer to the nearest tenth of a percent.

Found 2 solutions by Boreal, ikleyn:
Answer by Boreal(15235)   (Show Source): You can put this solution on YOUR website!
rule of 70 is 70/14=5%
P=6000(1+r)^14
12000=6000(1+r)^14
2=(1+r)^14
ln2=14 ln(1+r)
0.693=14 *ln(1+r)
.0495=ln (1+r)
raise everything to e power
1.051=(1+r)
r=0.051 or 5.1%
Answer by ikleyn(52767)   (Show Source): You can put this solution on YOUR website!
.
Let "x" be the interest rate under the question (as percentage).


Then, since it is SIMPLE INTEREST (according to the condition)


12000 = ,


which implies  2 =  = , 


x =  = 7.1%   (rounded to the nearest tenth of a percent).

Solved.


Be aware:   The solution by  @Boreal is   W R O N G   and   I R R E L E V A N T.


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