Question

on your own

1. the population of deer in a protected area is 225. if the population increases at a rate of 24% per year, how many deer will be in the area next year?
2. there are 75 students enrolled in a camp. the day before the camp begins, 8% of the students cancel. how many students actually attend the camp?
3. two years ago, a car was valued at $24,000. this year, the value of it is $23,160. what was the percent decrease in the value of the car?
4. mr. milton had $1,200 in his savings account at the beginning of the year. if his account has a balance of $1,230 at the end of the year, what is the percent increase of his balance?
5. last year, 140 people in a community had cell phones. this year, the number of people in the community with cell phones has increased by 65%. a. what is the percent of increase? b. what is the change in the number of people with cell phones? c. how many people in the community have cell phones this year?
6. a library has 300 feet of shelves for books.

Explanation:

Step1: Calculate deer population next year

The formula for population increase is $New\ population = Original\ population\times(1 + r)$, where $r$ is the rate of increase. Here, the original population of deer is 225 and the rate of increase $r = 0.24$. So, $New\ population=225\times(1 + 0.24)$.
$225\times1.24 = 279$

Step2: Calculate number of students attending camp

The number of students who cancel is $75\times0.08=6$. The number of students who attend is the original number of students minus the number of students who cancel. So, $75-6 = 69$

Step3: Calculate percent - decrease of car value

The formula for percent - decrease is $\text{Percent decrease}=\frac{\text{Original value}-\text{New value}}{\text{Original value}}\times100\%$. The original value of the car is $24000$ and the new value is $23160$. So, $\frac{24000 - 23160}{24000}\times100\%=\frac{840}{24000}\times100\% = 3.5\%$

Step4: Calculate percent - increase of savings balance

The formula for percent - increase is $\text{Percent increase}=\frac{\text{New value}-\text{Original value}}{\text{Original value}}\times100\%$. The original value is $1200$ and the new value is $1230$. So, $\frac{1230 - 1200}{1200}\times100\%=\frac{30}{1200}\times100\% = 2.5\%$

Step5A: Calculate percent - increase of cell - phone users

The number of new cell - phone users is $69$. The original number of cell - phone users is $140$. The percent - increase is $\frac{69}{140}\times100\%\approx49.29\%$

Step5B: Calculate change in number of cell - phone users

The change in the number of people with cell phones is given as 69

Step5C: Calculate current number of cell - phone users

The current number of cell - phone users is $140 + 69=209$

Answer:

1. 279
2. 69
3. 3.5%
4. 2.5%

10A. Approximately 49.29%
10B. 69
10C. 209