How do you increase/decrease by a percentage?
Convert % → decimal
Increase → multiply by (1 + %)
Decrease → multiply by (1 − %)
Example:
Increase 20 by 8% → 20 × 1.08
What does “of” mean?
Multiply
15% of 459 = ___ × ___
0.15 × 459
Profit formula?
Profit = Selling price − Cost price
% Profit = (___ ÷ ___) × 100
profit ÷ cost price
% Discount formula?
(discount ÷ cost price) × 100
Steps?
Identify P, r, n
Convert r → decimal
Use: I = Prn
In I = Prn:
P = ___
r = ___
n = ___
P = principal
r = rate (decimal)
n = time
🧠 FLOWCARD: Compound Interest
Front:
Steps?
Identify PV, r, n
Convert r → decimal
Use: FV = PV(1 + r)^n
Simple vs compound?
Simple = no compounding
Compound = interest on interest
Depreciation formula?
S = V₀(1 − r)^n
Depreciation uses (1 ___ r)
1 − r
$1000 depreciates 10% for 2 years → setup?
1000 × (0.9)^2
Gross vs net income?
Gross = total earned
Net = after deductions
Time and a half?
1.5 × hourly rate
Double time?
2 × hourly rate
Two types of expenses?
Fixed and variable
How to convert units?
km → m = ×1000
m → cm = ×100
cm → mm = ×10
Reverse = divide
Loan repayment?
Regular payment including loan + interest
Area conversion rule?
Square the conversion
Volume conversion rule?
Cube the conversion
Perimeter?
Distance around a shape
Distance around a shape
C = 2πr
C = πd
Area of circle?
A = πr²
