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6300 dollars is placed in an account with an annual interest rate of 6.5%. to the nearest tenth of a year, how long will it take for the account value to reach 28200 dollars?

1 Answer

2 votes

Answer:23.8

Step-by-step explanation:Exponential Functions:

y, equals, a, b, to the power x

y=ab

x

a, equals, starting value = , 6300

a=starting value = 6300

r, equals, rate = , 6, point, 5, percent, equals, 0, point, 0, 6, 5

r=rate = 6.5%=0.065

Exponential Growth:

Exponential Growth:

b, equals, 1, plus, r, equals, 1, plus, 0, point, 0, 6, 5, equals, 1, point, 0, 6, 5

b=1+r=1+0.065=1.065

Write Exponential Function:

Write Exponential Function:

y, equals, 6300, left bracket, 1, point, 0, 6, 5, right bracket, to the power x

y=6300(1.065)

x

Put it all together

Plug in y-value:

Plug in y-value:

28200, equals, 6300, left bracket, 1, point, 0, 6, 5, right bracket, to the power x

28200=6300(1.065)

x

start fraction, 28200, divided by, 6300, end fraction, equals, start fraction, 6300, left bracket, 1, point, 0, 6, 5, right bracket, to the power x , divided by, 6300, end fraction

6300

28200

=

6300

6300(1.065)

x

Divide both sides by 6300

4, point, 4, 7, 6, 1, 9, equals, 1, point, 0, 65, to the power x

4.47619=1.065

x

log, 4, point, 4, 7, 6, 1, 9, equals, log, 1, point, 0, 65, to the power x

log4.47619=log1.065

x

Take the log of both sides

log, 4, point, 4, 7, 6, 1, 9, equals, x, log, 1, point, 0, 6, 5

log4.47619=xlog1.065

Use power rule to bring x to the front

start fraction, log, 4, point, 4, 7, 6, 1, 9, divided by, log, 1, point, 0, 6, 5, end fraction, equals, start fraction, x, log, 1, point, 0, 6, 5, divided by, log, 1, point, 0, 6, 5, end fraction

log1.065

log4.47619

=

log1.065

xlog1.065

Divide both sides by log(1.065)

23, point, 7, 9, 9, 5, 5, 7, equals, x

23.799557=x

x, approximately equals, 23, point, 8

x≈23.8

User Justin Makeig
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