The answer is 168 seconds.
Answer:
Cost of One Journal = $3.99
Cost of One pen = $0.59
Step-by-step explanation:
Let
Cost of One Journal = x
Cost of One pen = y
We can make equation from given statements.
Mr. Bowden purchases 18 journals and 40 pencils for $95.42.
![18x+40y=95.42](https://tex.z-dn.net/?f=18x%2B40y%3D95.42)
Ms. Jacinto purchases 11 journals and 16 pencils for $53.33.
![11x+16y=53.33](https://tex.z-dn.net/?f=11x%2B16y%3D53.33)
Now solving these equations to find the value of x
![18x+40y=95.42--eq(1)\\11x+16y=53.33--eq(2)](https://tex.z-dn.net/?f=18x%2B40y%3D95.42--eq%281%29%5C%5C11x%2B16y%3D53.33--eq%282%29)
Multiply eq(1) with 2 and eq(2) with 5
![36x+80y=190.84\\55x+80y=266.65\\-\:\:\:\:-\:\:\:\;\:\:\:\:\:\:\:-\\---------\\-19x=-75.81\\x=\frac{-75.81}{-19}\\x=3.99\\](https://tex.z-dn.net/?f=36x%2B80y%3D190.84%5C%5C55x%2B80y%3D266.65%5C%5C-%5C%3A%5C%3A%5C%3A%5C%3A-%5C%3A%5C%3A%5C%3A%5C%3B%5C%3A%5C%3A%5C%3A%5C%3A%5C%3A%5C%3A%5C%3A-%5C%5C---------%5C%5C-19x%3D-75.81%5C%5Cx%3D%5Cfrac%7B-75.81%7D%7B-19%7D%5C%5Cx%3D3.99%5C%5C)
We get the value of x is: x=3.99
Now, putting value of x in equation 1 to find value of y.
![18x+40y=95.42\\18(3.99)+40y=95.42\\71.82+40y=95.42\\40y=95.42-71.82\\40y=23.6\\y=\frac{23.6}{40}\\y= 0.59](https://tex.z-dn.net/?f=18x%2B40y%3D95.42%5C%5C18%283.99%29%2B40y%3D95.42%5C%5C71.82%2B40y%3D95.42%5C%5C40y%3D95.42-71.82%5C%5C40y%3D23.6%5C%5Cy%3D%5Cfrac%7B23.6%7D%7B40%7D%5C%5Cy%3D%200.59)
So, we get the value of y: y = 0.59
Now, finding the costs:
Cost of One Journal = x = $3.99
Cost of One pen = y = $0.59
Invested amount (P) = $300.
Time in years (t) = 2 years.
Balance after 2 years (A) = $329.49.
Let us assume rate of interest = r % compounds annually.
We know, formula for compound interest
![A=P(1+r)^t](https://tex.z-dn.net/?f=A%3DP%281%2Br%29%5Et)
Plugging values in formula, we get
![329.49=300(1+r)^2](https://tex.z-dn.net/?f=329.49%3D300%281%2Br%29%5E2)
![\mathrm{Divide\:both\:sides\:by\:}300](https://tex.z-dn.net/?f=%5Cmathrm%7BDivide%5C%3Aboth%5C%3Asides%5C%3Aby%5C%3A%7D300)
![\frac{300\left(1+r\right)^2}{300}=\frac{329.49}{300}](https://tex.z-dn.net/?f=%5Cfrac%7B300%5Cleft%281%2Br%5Cright%29%5E2%7D%7B300%7D%3D%5Cfrac%7B329.49%7D%7B300%7D)
![\left(1+r\right)^2=1.0983](https://tex.z-dn.net/?f=%5Cleft%281%2Br%5Cright%29%5E2%3D1.0983)
Taking square root on both sides, we get
![1+r=\sqrt{1.0983}](https://tex.z-dn.net/?f=1%2Br%3D%5Csqrt%7B1.0983%7D)
![\mathrm{Subtract\:}1\mathrm{\:from\:both\:sides}](https://tex.z-dn.net/?f=%5Cmathrm%7BSubtract%5C%3A%7D1%5Cmathrm%7B%5C%3Afrom%5C%3Aboth%5C%3Asides%7D)
![1+r-1=\sqrt{1.0983}-1](https://tex.z-dn.net/?f=1%2Br-1%3D%5Csqrt%7B1.0983%7D-1)
![r=\sqrt{1.0983}-1](https://tex.z-dn.net/?f=r%3D%5Csqrt%7B1.0983%7D-1)
![r=1.048-1](https://tex.z-dn.net/?f=r%3D1.048-1)
r=0.048.
Converting it into percentage by multiplying by 100.
r=0.048 × 100
r = 4.8 %
Therefore, the rate of interest on the account is 4.8% compounds annually.
To make the inequality, we will use the ≥ sign to determine how many more tickets we will need. Before we write the inequality, let's see how much money was already made by the present tickets. 70 x 9.50 = $665.
We can write the inequality as $665 + $9.50t ≥ $1000 where t is the number of tickets sold. Now we can solve
$665 + $9.50t ≥ $1000, subtract 665
$9.50t ≥ $335. Now isolate the t by divide 9.50 to both sides
t ≥ 35.26 which we can round up to 36 because you cant sell 35.26 tickets.
So you need at least 36 more tickets to earn at least $1000