Proportions and Equations Remember that RATES in these equations must be expressed as decimals. Examples: 8% = .08 7.5% = .075 20% = .20 or .2 5.25% = .0525 OPTION A 12.5% = .125 π π’ππ‘ππ‘ππ π₯ π ππππ π‘ππ₯ πππ‘π = π ππππ π‘ππ₯ π π’ππ‘ππ‘ππ + π ππππ π‘ππ₯ = π‘ππ‘ππ OPTION B π π’ππ‘ππ‘ππ π₯ (1 + π ππππ π‘ππ₯ πππ‘π) = π‘ππ‘ππ π π’ππ‘ππ‘ππ π₯ ππππ‘π’ππ‘π¦/π‘ππ πππ‘π = ππππ‘π’ππ‘π¦/π‘ππ π π’ππ‘ππ‘ππ + ππππ‘π’ππ‘π¦/π‘ππ = π‘ππ‘ππ π‘ππ‘ππ π ππππ π₯ ππππππ π πππ πππ‘π = ππππππ π πππ πππ π πππ¦ + ππππππ π πππ = π‘ππ‘ππ π π’ππ‘ππ‘ππ π₯ πππ πππ‘π = πππ ππππ’ππ‘ π π’ππ‘ππ‘ππ + πππ ππππ’ππ‘ = π‘ππ‘ππ ππππππππ πππππ π₯ πππππ’π πππ‘π = πππππ’π ππππ’ππ‘ OPTION A ππππππππ πππππ + πππππ’π ππππ’ππ‘ = π‘ππ‘ππ OPTION B OPTION A ππππππππ πππππ π₯ (1 + πππππ’π πππ‘π) = π‘ππ‘ππ ππππππππ πππππ π₯ πππππππ€π/πππ πππ’ππ‘ πππ‘π = πππππππ€π/πππ πππ’ππ‘ ππππ’ππ‘ ππππππππ πππππ − πππππππ€ππππ πππ’ππ‘ ππππ’ππ‘ = πππππππ€π/πππ πππ’ππ‘ πππππ OPTION B ππππππππ πππππ π₯ (1 − πππππππ€π/πππ πππ’ππ‘ πππ‘π) = ππππππ€π/πππ πππ’ππ‘ πππππ Remember that RATES in these equations must be expressed as decimals. Examples: 8% = .08 7.5% = .075 20% = .20 or .2 5.25% = .0525 πΌ = πππ‘ 12.5% = .125 I = interest p = principal (original amount) r = rate (years) t = time (in YEARS) πππππππππ + πππ‘ππππ π‘ = π‘ππ‘ππ If the time is given in the problem in months instead of years, you can simply place the number of months over 12 in your equation. π Examples: 4 months would be ππ of a year π 9 would be ππ of a year πππ€ π΄πππ’ππ‘−ππππππππ π΄πππ’ππ‘ ππππππππ π΄πππ’ππ‘ ππππππππ π΄πππ’ππ‘−πππ€ π΄πππ’ππ‘ ππππππππ π΄πππ’ππ‘ | πΈπ π‘ππππ‘ππ ππππ’π –π΄ππ‘π’ππ ππππ’π π΄ππ‘π’ππ ππππ’π π₯ 100 π₯ 100 | π₯ 100