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Question:

Oscar ordered food delivery for his family dinner. The total of the order was $122.19. If he was charged a 7% service fee and gave a 15% tip on the bill after the service fee, what was the final total of his order?

A
$150.35

Explaination

Step 1: Interpret the Problem

In this problem we are given a monetary value that incurs a fee percentage and a tip percentage, to find a final cost amount.

We will do this in two parts. First, we will determine the fee percentage amount and add that to the initial monetary value.

When calculating a percentage amount, we multiply the percentage by the given total.
*Fee Percentage x Initial Total = Fee Percentage Amount*

Step 2: Convert the fee percent to a decimal

We do not use actual percentages when solving math problems so we have to change 7% into a decimal.

In order to change a percent into a decimal, we divide the percent by 100, which is the same as moving the decimal two spots to the left. Since there is no decimal in 7, we assume it is to the right of the ones place, so:

7% = 7. %

Now we can slide the decimal point two spaces left. Note, there will be an empty space between the decimal and the 7 which is filled by a 0.

7.% → 0.07

7% as a decimal is 0.07

Step 3: Determine the fee percentage amount and find the first total

Now that our percent has been turned into a decimal we can multiply:

0.07 × 122.19 = 8.5533

*Note: We will not be rounding here, we round at the end of the problem.

To determine our first total, we add the percentage fee amount to our initial amount.

122.19 + 8.5533 = 130.7433

Step 4: Convert the tip percent to a decimal

We do not use actual percentages when solving math problems so we have to change 15% into a decimal.

In order to change a percent into a decimal, we divide the percent by 100, which is the same as moving the decimal two spots to the left. Since there is no decimal in 15, we assume it is to the right of the ones place, so:

15% = 15. %

Now we can slide the decimal point two spaces left.

15.% → 0.15

15% as a decimal is 0.15.

Step 5: Determine the tip percentage amount and find the final total

Remember that we are finding the tip based on the bill after the service fee, so we will use the total amount calculated in step 3 here.

Now that our percent has been turned into a decimal we can multiply it with our first total:

0.15 × 130.7433 = 19.611495

*Note: We will not be rounding here, we round at the end of the problem.

To determine our final total, we add the tip percentage amount to our first total.

130.7433 + 19.611495 = 150.354795

When a math problem has a final answer that represents a monetary quantity, the final answer must be rounded to the nearest hundredth, unless otherwise directed.

150.354795 = $150.35

The final total of Oscar’s order was $150.35.

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