Frequently Asked Questions

To find X% of Y: divide X by 100, then multiply by Y (20% of 150 = 0.20 × 150 = 30). To find what percent X is of Y: divide X by Y and multiply by 100 (30 of 120 = 25%). For change: ((New − Old) ÷ Old) × 100.

Percentage points are the simple subtraction of two rates (6% − 4% = 2 points). Percent change is relative (2 ÷ 4 × 100 = 50% increase). Headlines sometimes blur them — check which is meant.

Subtract the old value from the new value, divide by the old value, and multiply by 100. A move from $50 to $65 is (15 ÷ 50) × 100 = 30%.

Multiply the original price by (1 − discount ÷ 100). A 25% discount on $80 is $80 × 0.75 = $60. The savings are $80 × 0.25 = $20.

Multiply the original price by the discount as a decimal: 30% off $240 saves $240 × 0.30 = $72, so you pay $168. The discount calculator shows both figures plus a visual breakdown.

No — they multiply. 20% off plus an extra 10% off is 0.80 × 0.90 = 0.72, meaning you pay 72% and save 28%, not 30%.

Multiply the bill by the rate as a decimal: 18% on $48.50 is 0.18 × $48.50 = $8.73, for a $57.23 total. Divide the total by people to split it. 15–20% is the standard US restaurant range.

Multiply the pre-tax price by (1 + rate ÷ 100). At 8%, $50 becomes $50 × 1.08 = $54.00. To remove tax from a total, divide instead: $108 ÷ 1.08 = $100.

Traditionally the pre-tax subtotal. Tipping on the after-tax total is also common and adds a bit extra. Either is fine — and always check for auto-gratuity on large parties first.

You earn returns on both your original money and previously earned returns, so growth accelerates. $1,000 at 10% becomes $1,100 after year one, then earns 10% on $1,100 ($110) in year two — that extra $10 is compounding.

Simple interest pays only on the original principal (straight-line growth). Compound interest pays on principal plus accumulated interest (accelerating curve). At 6% over 30 years, $5,000 reaches $14,000 simple vs. about $28,717 compounded.

No — they’re estimates assuming a constant rate. Real returns vary, can be negative, and are reduced by fees, taxes, and inflation. Use projections to compare habits, not as promises.

Record every outflow for 30 days using statements plus a notes app for cash, sort into 8–12 stable categories, review 5 minutes weekly and 15 minutes monthly — and make one concrete change per review. Our expense-tracking guide walks through the full system.

50/30/20: about 50% of take-home pay to needs, 30% to wants, 20% to savings and extra debt payments. Adjust the bands to your cost of living after one month of real data.

Start with $500, then build to one month of essential expenses, then toward 3–6 months. Keep it in a separate, accessible savings account and define “emergency” in writing before you need it.