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PROBLEM

7. The population of a town, P(t)P(t), is modelled by the function P(t)=6t2+110t+3000P(t)=6 t^{2}+110 t+3000, where tt is time in years. Note: t=0t=0 represents the year 2000.
a) When will the population reach 6000 ?
b) What will the population be in 2030?

STEP 1

1. The function P(t)=6t2+110t+3000 P(t) = 6t^2 + 110t + 3000 models the population of the town over time.
2. t=0 t = 0 corresponds to the year 2000.
3. To find when the population reaches 6000, we need to solve for t t when P(t)=6000 P(t) = 6000 .
4. To find the population in 2030, we need to evaluate P(t) P(t) at t=30 t = 30 .

STEP 2

1. Solve for t t when P(t)=6000 P(t) = 6000 .
2. Evaluate P(t) P(t) at t=30 t = 30 .

STEP 3

Set the population function equal to 6000 to find when the population reaches this number:
P(t)=6t2+110t+3000=6000 P(t) = 6t^2 + 110t + 3000 = 6000

STEP 4

Subtract 6000 from both sides to set the equation to zero:
6t2+110t+30006000=0 6t^2 + 110t + 3000 - 6000 = 0 6t2+110t3000=0 6t^2 + 110t - 3000 = 0

STEP 5

Solve the quadratic equation 6t2+110t3000=0 6t^2 + 110t - 3000 = 0 using the quadratic formula t=b±b24ac2a t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} , where a=6 a = 6 , b=110 b = 110 , and c=3000 c = -3000 .
Calculate the discriminant:
b24ac=11024×6×(3000) b^2 - 4ac = 110^2 - 4 \times 6 \times (-3000) =12100+72000 = 12100 + 72000 =84100 = 84100

STEP 6

Calculate the roots using the quadratic formula:
t=110±841002×6 t = \frac{-110 \pm \sqrt{84100}}{2 \times 6} t=110±29012 t = \frac{-110 \pm 290}{12} Calculate the two possible values for t t :
t1=110+29012=18012=15 t_1 = \frac{-110 + 290}{12} = \frac{180}{12} = 15 t2=11029012=40012=1003 t_2 = \frac{-110 - 290}{12} = \frac{-400}{12} = -\frac{100}{3} Since t t represents time in years and cannot be negative, we discard t2 t_2 .

STEP 7

To find the population in 2030, calculate t t for the year 2030. Since t=0 t = 0 corresponds to the year 2000, t=30 t = 30 corresponds to the year 2030.
Evaluate P(t) P(t) at t=30 t = 30 :
P(30)=6(30)2+110(30)+3000 P(30) = 6(30)^2 + 110(30) + 3000

SOLUTION

Calculate P(30) P(30) :
P(30)=6(900)+3300+3000 P(30) = 6(900) + 3300 + 3000 =5400+3300+3000 = 5400 + 3300 + 3000 =11700 = 11700 The population will reach 6000 in the year 2000+15=2015 2000 + 15 = 2015 .
The population in 2030 will be 11700.

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