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The 50/30/20 rule divides your after-tax income into three buckets: 50% for needs (rent, groceries, utilities), 30% for wants (dining out, entertainment, hobbies), and 20% for savings and debt repayment. It's a simple framework to balance enjoying life today while building financial security for tomorrow.

BMI (Body Mass Index) is calculated by dividing your weight in kilograms by the square of your height in meters. For adults, a BMI of 18.5–24.9 is considered normal weight, 25–29.9 is overweight, and 30 or above is obese. Note that BMI doesn't account for muscle mass, so athletes may have a high BMI while being very healthy.

The minimum down payment depends on the loan type: FHA loans require as little as 3.5% (with a 580+ credit score), conventional loans can go as low as 3%, and VA/USDA loans may require 0% for eligible buyers. However, putting down less than 20% on a conventional loan requires Private Mortgage Insurance (PMI), which adds to your monthly cost.

To find what percentage X is of Y: (X ÷ Y) × 100. For example, 45 out of 60 = (45 ÷ 60) × 100 = 75%. To find X% of Y: (X ÷ 100) × Y. For example, 15% of 80 = (15 ÷ 100) × 80 = 12. To find percentage change: ((New − Old) ÷ Old) × 100.

A quick way to calculate a 15% tip: move the decimal point one place left (10%), then add half of that (5%). For a $48 bill: 10% = $4.80, half = $2.40, so 15% tip = $7.20. For 20%: just double the 10% amount ($4.80 × 2 = $9.60). Standard tipping is 15–20% for good service, 20–25% for excellent service.