Question 1

What is 20% of $350?

Accepted Answer

20% of $350 = $350 × 0.20 = $70. Quick mental math: to find 20% of any number, move the decimal one place left (10%) and double it. 10% of $350 = $35. Double it = $70. For tip calculations: 20% of $85 = $17. 20% of $120 = $24. Memorizing 10% and then adjusting (half for 5%, double for 20%) covers most everyday percentage calculations without a calculator.

Question 2

How do I calculate percent change between two numbers?

Accepted Answer

Percent change = ((New Value − Old Value) ÷ Old Value) × 100. Example: stock goes from $45 to $62. Change = ($62 − $45) ÷ $45 = $17 ÷ $45 = 0.378 = 37.8% increase. If it goes from $62 to $45: ($45 − $62) ÷ $62 = −$17 ÷ $62 = −27.4% decrease. Note: a 37.8% gain followed by a 27.4% loss brings you back to approximately your starting point — gains and losses are not symmetrical in percentage terms.

Question 3

If a price increased 15%, what was the original price?

Accepted Answer

Original price = current price ÷ (1 + percent increase). If something costs $230 now and increased 15%: $230 ÷ 1.15 = $200 original price. This is useful for calculating pre-sale prices, pre-tax amounts, or pre-inflation values. Another application: if rent is $2,300/month and increased 8% from last year, original rent was $2,300 ÷ 1.08 = $2,130.

Question 4

How do I calculate what percent one number is of another?

Accepted Answer

Percent = (Part ÷ Whole) × 100. What percent is $35 of $140? $35 ÷ $140 = 0.25 = 25%. Application: you saved $120 out of a $600 goal — that's $120 ÷ $600 = 20% complete. Your department spent $87,000 of a $450,000 budget — $87,000 ÷ $450,000 = 19.3% of budget used. Percentage calculations appear everywhere in finance, business, and daily life — the formula is always part ÷ whole × 100.

Question 5

What is the difference between percentage points and percent change?

Accepted Answer

These are different and frequently confused. If an interest rate goes from 3% to 4%, it increased by 1 percentage point, but by 33% in relative terms (1 ÷ 3 = 33%). Politicians and media often use whichever framing supports their argument. '1 percentage point increase' and '33% increase' both describe the same change. For mortgages, credit card rates, and investment returns, changes are quoted in basis points (bps) — 1% = 100 basis points. A 25 bps rate cut = 0.25% cut.

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