What Is a Rate?

A rate is a ratio comparing two quantities with different units. Common rates compare amounts over time, distance, or quantity.

1. Hourly Rate of Pay

Hourly rate is the amount earned per hour. To find total earnings: \( \text{Earnings} = \text{Hourly Rate} \times \text{Hours Worked} \) To find hourly rate: \( \text{Hourly Rate} = \frac{\text{Total Pay}}{\text{Hours Worked}} \)

2. Exchange Rates Between Currencies

Exchange rates tell you how much one currency is worth in another. To convert: \( \text{Amount in New Currency} = \text{Original Amount} \times \text{Exchange Rate} \) For example, if \$1 = €0.85, then \$100 = €85.

3. Flow Rates

Flow rate measures the volume of fluid that moves per unit of time. Typical units: litres per minute (L/min), millilitres per second (mL/s), etc. Formula: \( \text{Flow Rate} = \frac{\text{Volume}}{\text{Time}} \) or \( \text{Volume} = \text{Flow Rate} \times \text{Time} \)

4. Fuel Consumption

Fuel consumption tells how much fuel is used per distance travelled. Common units: – Litres per 100 kilometres (L/100 km) – Miles per gallon (mpg) Formulas: \( \text{Fuel Used} = \frac{\text{Distance Travelled} \times \text{Rate}}{100} \) or \( \text{Fuel Efficiency} = \frac{\text{Distance}}{\text{Fuel Used}} \)

Important:

• Always check the units — convert them if necessary before using formulas.
• Rates are used in real-world financial, travel, engineering, and science contexts.
• If rates are given per 1 unit (e.g. per hour), simply multiply or divide accordingly.