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in 2011 a country\'s federal receipts (money taken in) totaled $2.36trillion. In

ID: 2850262 • Letter: I

Question

in 2011 a country's federal receipts (money taken in) totaled $2.36trillion. In 2013, total federal receipts were

$2.68 trillion. Assume that the growth of federal receipts, F, can be modeled by an exponential function and use 2011 as the base year (t=0).

a)

Find the growth rate k to six decimal places, and write the exponential function F(t), for total receipts in trillions of dollars.

b)

Estimate total federal receipts in 2015.

c)

When will total federal receipts be $12 trillion?

a)

Find the growth rate k to six decimal places, and write the exponential function F(t), for total receipts in trillions of dollars.

b)

Estimate total federal receipts in 2015.

c)

When will total federal receipts be $12 trillion?

Explanation / Answer

general form of exponential function is y=aekt

1)in 2011, t=0

In 2011, total federal receipts were $2.36 trillion

2.36 =ae0

a=2.36

y=2.36ekt

In 2013, total federal receipts were $2.68 trillion

in 2013, t=2

2.68=2.36ek*2

ek*2=2.68/2.36

2k=ln(2.68/2.36)

k=(1/2)ln(2.68/2.36)

k=0.063578

f(t)=y=2.36e0.063578t

b)t=2015-2011=4

f(4)=y=2.36e0.063578*4

f(4)=3.04trillion

c)12=2.36e0.063578t

e0.063578t=12/2.36

0.063578t=ln(12/2.36)

t=[ln(12/2.36)]/0.063578

t=25.6

t=26

in the year 2011+26=2037 total federal receipts be $12 trillion