How Do You Calculate a Percentage of a Number

Percentage of a Number Calculator

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How to Calculate a Percentage of a Number

Calculating a percentage of a number is one of the most useful mathematical skills in daily life. Whether you are trying to find the discount on a jacket, calculating sales tax, or determining a tip at a restaurant, the process is straightforward.

The Basic Formula

The standard formula for finding a percentage of a number is:

(Percentage / 100) × Number = Result

Step-by-Step Instructions

  1. Convert the percentage to a decimal: Divide the percentage by 100. For example, 25% becomes 0.25 (25 ÷ 100 = 0.25).
  2. Multiply by the whole number: Multiply that decimal by the number you are interested in. For example, if you want 25% of 80, multiply 0.25 by 80.
  3. The result: 0.25 × 80 = 20.

Real-World Examples

  • Shopping Discounts: If a shirt costs 40 and is 15% off, calculate 15% of 40 (0.15 × 40 = 6). The discount is 6.
  • Tipping: If your bill is 60 and you want to leave a 20% tip, calculate 20% of 60 (0.20 × 60 = 12). The tip is 12.
  • Performance Grades: If an exam has 50 questions and you got an 80%, calculate 80% of 50 (0.80 × 50 = 40). You got 40 answers correct.

Common Percentage Benchmarks

Percentage Decimal Equivalent Fraction Equivalent
10% 0.1 1/10
25% 0.25 1/4
50% 0.5 1/2
75% 0.75 3/4
function calculatePercentage() { var perc = document.getElementById('percentageVal').value; var num = document.getElementById('wholeNumberVal').value; var resultBox = document.getElementById('calc-result-box'); var resultText = document.getElementById('resultText'); var explanationText = document.getElementById('explanationText'); if (perc === " || num === ") { alert('Please enter both values.'); return; } var p = parseFloat(perc); var n = parseFloat(num); if (isNaN(p) || isNaN(n)) { alert('Please enter valid numerical values.'); return; } // Logic: (p / 100) * n var result = (p / 100) * n; // Formatting result to avoid excessive decimals var formattedResult = Number.isInteger(result) ? result : result.toFixed(4).replace(/\.?0+$/, ""); resultText.innerHTML = formattedResult; explanationText.innerHTML = p + "% of " + n + " is exactly " + formattedResult + "."; resultBox.style.display = 'block'; }

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