Frequently Asked Questions

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.

Daily calorie needs depend on age, sex, height, weight, and activity level. As a general guide: sedentary adult women need about 1,600–2,000 calories; sedentary adult men need about 2,000–2,400 calories. Active individuals need significantly more. Use a TDEE (Total Daily Energy Expenditure) calculator for a personalized estimate.

The commonly cited guideline is about 8 cups (2 liters) per day, but individual needs vary. A more precise formula is to drink 30–35 ml per kilogram of body weight. Active people, those in hot climates, and pregnant or breastfeeding women need more. Your urine color is a good indicator — pale yellow means you're well hydrated.

The CDC recommends that adults aged 18–60 get at least 7 hours of sleep per night. Adults aged 61–64 need 7–9 hours, and those 65 and older need 7–8 hours. Consistently getting less than 7 hours is linked to increased risk of obesity, diabetes, heart disease, and mental health issues.

A normal resting heart rate for adults is 60–100 beats per minute (bpm). Athletes and very fit individuals often have resting heart rates of 40–60 bpm, which indicates a strong, efficient heart. A consistently high resting heart rate (above 100 bpm) may indicate stress, dehydration, or an underlying health condition worth discussing with a doctor.

The most common formula is: Maximum Heart Rate = 220 − your age. For example, a 35-year-old has an estimated max heart rate of 185 bpm. For moderate-intensity exercise, aim for 50–70% of your max heart rate. For vigorous exercise, aim for 70–85%. These zones help you exercise safely and effectively.

The WHO recommends adults get at least 150–300 minutes of moderate-intensity aerobic activity per week (like brisk walking), or 75–150 minutes of vigorous-intensity activity (like running). Additionally, do muscle-strengthening activities (like weight training) on 2 or more days per week. Even small amounts of movement are better than none.

The general recommendation is 0.8 grams of protein per kilogram of body weight for sedentary adults. If you're active or trying to build muscle, aim for 1.2–2.0 grams per kilogram. For a 70 kg (154 lb) person, that's 56–140 grams of protein per day depending on activity level. Good sources include meat, fish, eggs, dairy, legumes, and tofu.

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.

The 28/36 rule is a guideline lenders use to assess affordability. Your monthly housing costs (mortgage, taxes, insurance) should not exceed 28% of your gross monthly income. Your total debt payments (housing plus car loans, student loans, credit cards) should not exceed 36% of gross income. Staying within these limits reduces financial stress.

It depends on your financial situation, lifestyle, and local market. Buying builds equity and offers stability, but requires a large upfront cost and ties up capital. Renting offers flexibility and lower upfront costs, but you don't build equity. A common rule of thumb: if the price-to-rent ratio in your area is above 20, renting may be more economical.

Closing costs are fees paid at the end of a real estate transaction, typically 2–5% of the loan amount. They include lender fees (origination, appraisal), title insurance, attorney fees, prepaid taxes and insurance, and recording fees. On a $300,000 home, expect to pay $6,000–$15,000 in closing costs in addition to your down payment.

Home equity is the portion of your home's value that you own outright: Current Market Value − Outstanding Mortgage Balance. You can access equity through a Home Equity Loan (lump sum at fixed rate), a HELOC (revolving credit line), or a cash-out refinance. Common uses include home improvements, debt consolidation, or funding education.

Amortization is the process of paying off your mortgage through regular payments over time. Each payment covers both interest and principal. In the early years, most of your payment goes toward interest. As the loan balance decreases, more of each payment goes toward principal. A 30-year mortgage amortization table shows exactly how each payment is split.

Most lenders prefer a debt-to-income (DTI) ratio of 43% or lower for mortgage approval. Your DTI is calculated by dividing your total monthly debt payments by your gross monthly income. A DTI below 36% is considered excellent. Lower DTI means you have more income available relative to your debt, making you a lower-risk borrower.

Property taxes are annual taxes levied by local governments based on the assessed value of your property. The tax rate (mill rate) varies widely by location — typically 0.5–2.5% of assessed value per year. For a $400,000 home at a 1.2% rate, you'd pay $4,800 per year ($400/month). Property taxes are often included in your monthly mortgage escrow payment.

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.

The compound interest formula is: A = P(1 + r/n)^(nt), where A = final amount, P = principal, r = annual interest rate (as a decimal), n = number of times interest compounds per year, and t = time in years. For example, $1,000 at 5% compounded monthly for 10 years: A = 1000(1 + 0.05/12)^(12×10) ≈ $1,647.

Rectangle: length × width. Triangle: (base × height) ÷ 2. Circle: π × radius². Trapezoid: ((base1 + base2) × height) ÷ 2. For example, a circle with radius 5 has area = π × 25 ≈ 78.54 square units. For irregular shapes, divide them into simpler shapes and add the areas together.

The Pythagorean theorem states that in a right triangle, the square of the hypotenuse (the side opposite the right angle) equals the sum of the squares of the other two sides: a² + b² = c². For example, if a = 3 and b = 4, then c = √(9 + 16) = √25 = 5. This is useful for calculating distances and in construction.

Common conversions: 1 inch = 2.54 cm; 1 foot = 0.3048 m; 1 mile = 1.609 km; 1 pound = 0.4536 kg; 1 gallon = 3.785 liters; 1 ounce = 28.35 grams. For temperature: °F = (°C × 9/5) + 32; °C = (°F − 32) × 5/9. For example, 100°C = 212°F (boiling point of water).

The order of operations determines which calculations to perform first: Parentheses/Brackets first, then Exponents/Orders, then Multiplication and Division (left to right), then Addition and Subtraction (left to right). For example: 2 + 3 × 4² = 2 + 3 × 16 = 2 + 48 = 50. Without following the order, you'd get the wrong answer.

Mean (average): sum all values, divide by count. Median: sort values, find the middle one (or average of two middle values for even count). Mode: the value that appears most frequently. For the dataset {2, 4, 4, 6, 8}: Mean = 24/5 = 4.8; Median = 4; Mode = 4. Each measure describes the 'center' of data differently.

Simple interest is calculated only on the original principal: Interest = P × r × t. Compound interest is calculated on the principal plus accumulated interest. For $1,000 at 5% over 3 years: Simple interest = $1,000 × 0.05 × 3 = $150 total interest. Compound interest (annual) = $1,000 × (1.05)³ − $1,000 ≈ $157.63. The difference grows significantly over longer periods.

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.

To find the sale price after a discount: Sale Price = Original Price × (1 − Discount%). For a $120 item with 25% off: $120 × (1 − 0.25) = $120 × 0.75 = $90. To find the discount amount: $120 × 0.25 = $30. When comparing 'buy one get one 50% off' vs '25% off everything,' calculate the total for your specific purchase to find the better deal.

Common US cooking conversions: 3 teaspoons = 1 tablespoon; 16 tablespoons = 1 cup; 1 cup = 8 fluid ounces = 240 ml; 4 cups = 1 quart; 4 quarts = 1 gallon. For metric: 1 cup ≈ 240 ml; 1 tablespoon ≈ 15 ml; 1 teaspoon ≈ 5 ml. When scaling recipes, multiply all ingredient quantities by the same factor.

Fuel efficiency (MPG): Miles driven ÷ Gallons used. Trip fuel cost: (Distance ÷ MPG) × Price per gallon. For a 300-mile trip in a car getting 30 MPG with gas at $3.50/gallon: (300 ÷ 30) × $3.50 = 10 × $3.50 = $35. To compare two vehicles, calculate the annual fuel cost difference based on your typical mileage.

Electricity cost = (Wattage ÷ 1000) × Hours used × Cost per kWh. For a 100-watt bulb running 8 hours/day at $0.12/kWh: (100 ÷ 1000) × 8 × $0.12 = $0.096/day = about $35/year. A 1,500-watt space heater running 4 hours/day costs (1500 ÷ 1000) × 4 × $0.12 = $0.72/day = about $263/year.

Cost per unit = Total Price ÷ Quantity. For example, a 32 oz bottle for $4.00 costs $4.00 ÷ 32 = $0.125 per oz. A 20 oz bottle for $2.80 costs $2.80 ÷ 20 = $0.14 per oz. The larger bottle is cheaper per ounce. Always compare the same unit (per oz, per gram, per count) to find the true best value.

If you only make minimum payments, it can take decades to pay off a credit card. To estimate payoff time: use the formula n = −log(1 − (r × B) / P) / log(1 + r), where B = balance, r = monthly interest rate, P = monthly payment. For a $3,000 balance at 20% APR paying $100/month: it takes about 44 months and costs ~$1,400 in interest. Paying $200/month cuts it to 18 months.

For a rectangular room: Area = Length × Width. For an L-shaped room, divide it into two rectangles and add the areas. Always add 10% extra for waste and cuts. For a 12 ft × 15 ft room: 180 sq ft + 10% = 198 sq ft to purchase. If flooring costs $3.50/sq ft, budget 198 × $3.50 = $693 for materials, plus installation costs.

GPA (Grade Point Average) is calculated by multiplying each course's grade points by its credit hours, summing all those values, then dividing by total credit hours. Grade points: A=4.0, B=3.0, C=2.0, D=1.0, F=0. For example: an A in a 3-credit course (12 points) + a B in a 4-credit course (12 points) = 24 points ÷ 7 credits = 3.43 GPA.

Student loans are borrowed money that must be repaid with interest. Federal loans (subsidized and unsubsidized) have fixed rates set by Congress and offer income-driven repayment plans. Subsidized loans don't accrue interest while you're in school. Private loans have variable or fixed rates based on your credit. Always exhaust federal loan options before taking private loans.

Research-backed study strategies include: spaced repetition (reviewing material at increasing intervals), active recall (testing yourself rather than re-reading), the Pomodoro technique (25 minutes focused study, 5-minute break), teaching concepts to others, and getting adequate sleep before exams. Avoid cramming — distributed practice over days is far more effective than one long session.

ROI = (Lifetime Earnings Increase − Total Education Cost) ÷ Total Education Cost × 100%. Consider: total tuition and fees, opportunity cost (income foregone while studying), and the salary premium your degree provides over a lifetime. On average, a bachelor's degree holder earns about $1 million more over a lifetime than a high school graduate, but this varies greatly by field and institution.

Scholarships are merit-based awards that don't need to be repaid — they're earned through academic achievement, talent, or other criteria. Grants are need-based awards that also don't require repayment — the Pell Grant is the most common federal grant. Loans must be repaid with interest. Always prioritize free money (scholarships and grants) before taking on loans.

A common guideline: your total student loan debt should not exceed your expected first-year salary. If you expect to earn $45,000 after graduation, try to borrow no more than $45,000 total. With a standard 10-year repayment plan, monthly payments are roughly 1% of total debt — so $45,000 in loans means about $450/month, which is manageable on a $45,000 salary.

A 529 plan is a tax-advantaged savings account designed for education expenses. Contributions grow tax-free, and withdrawals for qualified education expenses (tuition, books, room and board) are also tax-free. Many states offer additional tax deductions for contributions. You can use 529 funds at most accredited colleges, universities, and vocational schools in the US.

Effective strategies include: taking a full-length practice test first to identify weak areas, focusing study time on your weakest subjects, learning test-taking strategies specific to each section, practicing with official materials (College Board for SAT, ACT Inc. for ACT), and taking the test multiple times if needed. Most students improve their score by 50–150 points with 3 months of consistent preparation.