In 2000, the population at Arlington middle school was approximately 421 students. In 2010, the population was approximately 584 students. Find the percent of change in the population at Arlington middle school from 2000 to 2010 and identify it as an increase or decrease.

A:27.9%; increase
B:27.9%; decrease
C:38.7%; increase
D:38.7%; decrease

2.The owner of an electronic store received a shipment of MP3 players at a cost of $64.25 each. If he sells the MP3 players for $99.99 each, what is the percent of the markup? Round to the nearest whole percent.
A:6%
B:36%
C:56%
D:62%

3.Find the final balance in an account with $730 invested at 3% annual simple interest for four years.
A:$735.48
B:$87.60
C:$817.60
D:$8,760.00

How do I solve these?

To answer the first question, you can calculate the percent of change by using the formula:

Percent of Change = (New Value - Initial Value) / Initial Value * 100

1. Calculate the percent of change in population at Arlington middle school from 2000 to 2010:
New Value = 584 students
Initial Value = 421 students

Percent of Change = (584 - 421) / 421 * 100
Percent of Change = 163 / 421 * 100
Percent of Change = 0.387 * 100
Percent of Change = 38.7%

Therefore, the correct answer is C: 38.7%; increase.

For the second question, you can calculate the percent markup by using the formula:

Percent Markup = (Selling Price - Cost Price) / Cost Price * 100

2. Calculate the percent of markup for the MP3 players:
Selling Price = $99.99
Cost Price = $64.25

Percent Markup = ($99.99 - $64.25) / $64.25 * 100
Percent Markup = $35.74 / $64.25 * 100
Percent Markup = 0.556 * 100
Percent Markup = 55.6%

Rounding to the nearest whole percent, the correct answer is C: 56%.

For the third question, you can calculate the final balance using the formula for simple interest:

Final Balance = Initial Balance + (Initial Balance * Interest Rate * Time)

3. Calculate the final balance in the account:
Initial Balance = $730
Interest Rate = 3% (convert to decimal = 0.03)
Time = 4 years

Final Balance = $730 + ($730 * 0.03 * 4)
Final Balance = $730 + ($730 * 0.12)
Final Balance = $730 + $87.60
Final Balance = $817.60

Therefore, the correct answer is C: $817.60.

To solve these problems, we'll go through each one step-by-step:

1. Finding the percent of change:
First, we need to calculate the difference in the population between 2000 and 2010. We subtract the population in 2000 (421) from the population in 2010 (584): 584 - 421 = 163.

Next, we calculate the percent change by dividing the difference by the initial population (421) and then multiplying by 100 to get the percentage: (163 / 421) * 100.

To determine if it's an increase or decrease, we will compare the population in 2010 with the population in 2000. Since the population in 2010 (584) is larger than the population in 2000 (421), it is an increase.

Calculating the percent of change using the formula: (163 / 421) * 100 gives us approximately 38.7. Therefore, the correct answer is option D: 38.7% increase.

2. Finding the percent of markup:
To calculate the markup percentage, we need to find the difference between the selling price and the cost price. The difference is $99.99 - $64.25 = $35.74.

Next, we find the percentage markup by dividing the difference by the cost price and multiplying by 100: ($35.74 / $64.25) * 100.

Rounding to the nearest whole percentage gives us approximately 55.71%. Since we need to round to the nearest whole percent, the answer is 56%.

Therefore, the correct answer is option C: 56%.

3. Calculating the final balance with simple interest:
To find the final balance in an account with simple interest, we use the formula: Balance = Principal + (Principal * Rate * Time).

Given:
Principal (P) = $730
Rate (R) = 3% (expressed as a decimal, 0.03)
Time (T) = 4 years

We'll plug these values into the formula:
Balance = $730 + ($730 * 0.03 * 4).

Simplifying the equation:
Balance = $730 + ($730 * 0.12).

Balance = $730 + $87.60 = $817.60.

Therefore, the correct answer is option C: $817.60.

To solve similar problems in the future, use the given formulas and plug in the provided values. Compute the calculations step-by-step, making sure to round to the appropriate decimal places or whole percentages as needed.

1.

584 - 421 = 163

100 * (163/421) = ________

2. Try this one yourself.

3. Start with the formula: Interest = principle times rate times time

I'll be glad to check your answers.