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To calculate percentages effectively, we must first convert them into decimal form. This is a fundamental skill because most mathematical operations with percentages involve multiplication, which is easier with decimals. Percentages represent a fraction out of 100. For instance, when you see 15%, it literally means 15 out of 100. To convert this into a decimal, we divide by 100. Hence, for 15%, the conversion would be:\[0.15 = \frac{15}{100}\]This step transforms the problem into one that algebra can more readily handle, as decimals are simpler to work with in equations. Remember, any percentage can be converted by simply moving the decimal point two places to the left.

Once we have a decimal, the next step is to use it to find a percentage of a total. This involves multiplication. In the context of our exercise, we want to find 15% of a bill that amounts to $32.50. We've already converted 15% into the decimal 0.15. Now, we perform the multiplication:\[0.15 \times 32.50\]In decimal multiplication, align the numbers by the decimal points and multiply as if they were whole numbers. After multiplying, count the total number of decimal places in both of the numbers being multiplied. For instance, here we have two decimal places in 0.15 and two in 32.50, making it four decimal places in total for the answer. This calculation gives us 4.875, the unrounded tip amount. Calculating decimals might seem tricky at first, but regular practice will make it second nature.

After calculating, the last step is rounding. Rounding makes numbers easier to handle and understand, especially when dealing with money. With monetary values, it's standard to round to two decimal places, because that's how cents are counted.Our calculation gave us 4.875. In rounding rules, if the digit after the second decimal place is 5 or more, you round up. Therefore, since the third decimal is 5, we round up:\[4.88 = \text{round}(4.875)\]This gives us a rounded tip amount of $4.88. Rounding helps to simplify the number without changing its value significantly, making it practical for everyday use like leaving a tip.