8. what mass of water in grams will fill a tank 100 cm long, 50 cm wide, and 30 cm high?\n9. the population…

Explanation:

Step1: Calculate volume of tank

The volume $V$ of a rectangular - prism tank is given by $V = l\times w\times h$, where $l = 100$ cm, $w = 50$ cm, and $h = 30$ cm. So $V=100\times50\times30 = 150000$ $cm^{3}$.

Step2: Use density of water

The density of water $\rho = 1$ g/$cm^{3}$. The mass $m$ of a substance is given by $m=\rho V$. Substituting $\rho = 1$ g/$cm^{3}$ and $V = 150000$ $cm^{3}$, we get $m = 1\times150000=150000$ g.

Step3: Calculate population in 1980

The population density formula is $D=\frac{P}{A}$, where $D$ is density, $P$ is population, and $A$ is area. Given $D = 1253$ people per square - mile and $A = 750$ square miles in 1980. Then $P=D\times A=1253\times750 = 939750$ people.

Step4: Calculate population in 2010

In 2010, $D = 1498$ people per square - mile and $A = 750$ square miles. So $P_{2010}=1498\times750=1123500$ people.

Step5: Calculate population change

The population change $\Delta P=P_{2010}-P_{1980}=1123500 - 939750=183750$ people.

Step6: Calculate population in 1990 and 2000

In 1990, $P_{1990}=1387\times750 = 1040250$ people. In 2000, $P_{2000}=1405\times750=1053750$ people.

Step7: Calculate percentage increase for each decade

For 1980 - 1990: $\text{Percentage increase}=\frac{P_{1990}-P_{1980}}{P_{1980}}\times100=\frac{1040250 - 939750}{939750}\times100\approx10.7%$. For 1990 - 2000: $\text{Percentage increase}=\frac{P_{2000}-P_{1990}}{P_{1990}}\times100=\frac{1053750 - 1040250}{1040250}\times100\approx1.3%$. For 2000 - 2010: $\text{Percentage increase}=\frac{P_{2010}-P_{2000}}{P_{2000}}\times100=\frac{1123500 - 1053750}{1053750}\times100\approx6.6%$.

Answer:

8. 150000 g

a. 939750 people b. 183750 people c. 1990 - 2000 decade