This question tests finding the percent of a quantity, such as calculating 30% of 80 tickets to determine how many were sold to students, using the rate 30/100 multiplied by the quantity, which equals 24. Percent means per hundred, so 30% is 30 per 100 or 0.30 as a decimal; to find the part, multiply the decimal by the whole quantity, like 0.30 × 80 = 24. For example, 30% of 80 is calculated by converting 30% to 0.30 and multiplying by 80 to get 24, meaning 24 student tickets were sold. The correct calculation is 0.30 × 80 = 24, so the answer is 24. A common error is treating the percent as a whole number without converting, like multiplying 30 × 80 = 2400, or dividing instead of multiplying, such as 80 ÷ 30 = about 2.67. To find the part: (1) convert percent to decimal (30% → 0.30), (2) multiply by the quantity (0.30 × 80 = 24), (3) interpret that 24 tickets were sold to students. Remember common percents like 10% = 0.10, 25% = 0.25, and apply in contexts like ticket sales or portions of groups.

This question tests finding a percent of a quantity, such as calculating 30% of 80, which equals 24 using the rate $30/100$ multiplied by the quantity. Percent means a rate per 100, so 30% is 30 per 100 or 0.30 as a decimal (convert by dividing 30 by 100), and to find the part, multiply the decimal by the quantity: $0.30 \times 80 = 24$, or using fractions, $30/100 \times 80 = 2400/100 = 24$. For example, to find 30% of 80, convert 30% to 0.30 and multiply by 80 to get 24, which means 24 is the portion representing 30% of the total 80 points. The correct calculation is 30% of 80: $0.30 \times 80 = 24$, so the answer is 24. A common error is treating the percent as a whole number without converting, like multiplying $30 \times 80 = 2400$, or dividing instead of multiplying, such as $80 \div 30 = \text{about } 2.67$, or confusing it with 3% instead of 30% leading to $0.03 \times 80 = 2.4$. To find a percent of a quantity, first convert the percent to a decimal by dividing by 100 ($30% = 0.30$), then multiply by the quantity ($0.30 \times 80 = 24$), and interpret the result as the part of the whole. Common percents include $10% = 0.10$, $25% = 0.25$, and $50% = 0.50$; in contexts like test scores, this helps determine portions, but avoid mistakes like forgetting to convert the percent to a decimal.

This question tests finding the percent of a quantity, like 10% of 200 beads that are blue, calculated as 0.10 × 200 = 20. Percent means per hundred, so 10% is 0.10; multiply by the total to get the part, 0.10 × 200 = 20. For example, 10% of 200 is 0.10 × 200 = 20 blue beads. The correct calculation is 0.10 × 200 = 20, so 20 blue beads. Common errors include dividing 200 ÷ 10 = 20 but forgetting it's percent, or using 10 as 10.0 × 200 = 2000. To find the part: (1) convert percent to decimal (10% → 0.10), (2) multiply by quantity (0.10 × 200 = 20), (3) interpret as 20 blue. Easy percents like 10% are common in portions of sets.

This question tests finding a percent of a quantity, such as 75% of 36 marbles equals 27 blue ones using 75/100 × 36. Percent means per 100, so 75% = 0.75, and multiply 0.75 × 36 = 27; fractions work too: 75/100 = 3/4, and 3/4 × 36 = 27. For example, 75% of 36: 0.75 × 36 = 27 blue marbles. The correct calculation is 0.75 × 36 = 27, so there are 27 blue marbles. A common error is using 75 as whole: 75 × 36 = 2700, or dividing 36 ÷ 75 = 0.48, or mistaking for 7.5% = 0.075 × 36 ≈ 2.7. To find the part, convert percent to decimal (75% = 0.75), multiply by quantity (0.75 × 36 = 27), and verify. Remember 75% = 0.75 in contexts like proportions, avoiding decimal errors like using 0.075.

This question tests finding the whole given a part and percent, where 40 ounces are 50% of the bottle's capacity, so full capacity is 40 ÷ 0.50 = 80 ounces. Percent as a rate: 50% is 0.50; solve 0.50 × w = 40 by dividing w = 40 ÷ 0.50 = 80. For example, if 40 is 50% full, the full capacity is 40 ÷ 0.50 = 80 ounces. The correct calculation is 40 ÷ 0.50 = 80, so 80 ounces. A common mistake is multiplying 40 × 0.50 = 20 instead of dividing, or thinking 50% means half so wrongly halving. To find the whole: (1) convert percent to decimal (50% → 0.50), (2) set up 0.50 × w = 40, (3) divide 40 ÷ 0.50 = 80, (4) verify 0.50 × 80 = 40. Useful for capacities and fillings.

This question tests finding the whole given a part and its percent, where 18 made free throws are 75% of total attempts. Percent is per hundred, so 75% = 0.75. Divide the part by the rate: 18 ÷ 0.75 = 24. Set up 0.75 × a = 18 and solve for a. Errors include multiplying 18 × 0.75 = 13.5 or using 75 as 7.5. Steps: identify 18 as 75% or 0.75, divide 18 by 0.75 to get 24, verify 0.75 × 24 = 18. Useful in sports stats, remember 75% = 0.75.

This question tests finding the percent of a quantity, calculating 40% of 90 canned goods collected on the last day. Percent is per hundred, so 40% = 0.40. Multiply 0.40 by 90 to get 36. Or (40/100) × 90 = 36. Errors include multiplying by 40 to get 3600 or dividing 90 by 40 to get 2.25. Steps: convert 40% to 0.40, multiply by 90 for 36, and understand 36 cans on the last day. Applies to collections or drives, remember 40% = 0.40.

This question tests finding the percent of a quantity in a real-world context, like calculating a 15% tip on a $60 meal, using $ 15/100 \times 60 = 9 $. Percent means per hundred, so 15% is 0.15; multiply by the quantity to find the tip, $ 0.15 \times 60 = 9 $. For example, a 15% tip on $60 is $ 0.15 \times 60 = 9 $. The correct calculation is $ 0.15 \times 60 = 9 $, so the tip is $9. Common errors include forgetting to convert percent to decimal, like $ 15 \times 60 = 900 $, or using the wrong decimal like $ 0.015 \times 60 = 0.90 $. To find the part: (1) convert percent to decimal ($ 15% \to 0.15 $), (2) multiply by the cost ($ 0.15 \times 60 = 9 $), (3) interpret as $9 tip. Tips are a common percent application, along with discounts and taxes.

This question tests finding the percent of a quantity, such as 75% of 120 questions answered correctly, calculated as 0.75 × 120 = 90. Percent means per hundred, so 75% is 0.75; multiply by the total to find the part, 0.75 × 120 = 90. For example, 75% of 120 is 0.75 × 120 = 90 correct answers. The correct calculation is 0.75 × 120 = 90, so 90 questions. Common mistakes include using 75 as a whole number like 75 × 120 = 9000, or dividing 120 ÷ 75 = 1.6. To find the part: (1) convert percent to decimal (75% → 0.75), (2) multiply by quantity (0.75 × 120 = 90), (3) interpret as 90 correct. Memorize conversions like 75% = 0.75 for scores and tests.

This question tests finding the percent of a quantity, such as 20% of 150 levels completed, calculated as 0.20 × 150 = 30. Percent as a rate per 100: 20% is 0.20; multiply by the total, 0.20 × 150 = 30. For example, 20% of 150 is 0.20 × 150 = 30 levels. The correct calculation is 0.20 × 150 = 30, so 30 levels completed. A common error is using 20 as whole number like 20 × 150 = 3000, or dividing 150 ÷ 20 = 7.5. To find the part: (1) convert percent to decimal (20% → 0.20), (2) multiply by quantity (0.20 × 150 = 30), (3) interpret as 30 completed. Applies to progress like in games or tasks.