Big Numbers in the Economy: Estimate GDP, Inflation Math, and Compound Interest

Sixty-three questions that turn the economy's most quoted numbers into math you can actually do in your head. Three pillars: estimating GDP (the C + I + G + (X − M) identity, real vs. nominal, the GDP deflator, per-capita arithmetic, and the famous 2023 figures), inflation math (reading the CPI, the Rule of 70, real interest rates, and what hyperinflation really means), and compound interest (the Rule of 72, doubling time, CAGR, APR vs. APY, and continuous compounding with e). Most answers are numeric so you practice the calculation, not just recognition. Every explanation is followed by a Wikipedia or primary-source reference (BEA or the Federal Reserve) so you can verify the figure and read further — and a few questions deliberately debunk a popular but false 'fact'.