# Rates

You've probably encountered rates before in your life. Rates can be tricky to understand at first. However, they can be very useful in expressing a number of real-world concepts. Let's find out more about rates:

## What are rates?

Rates are numbers that express quantities in two different units. The basic rule of rates is that when you spell them out, they contain the word "per."

For example, you've probably heard of speed limits, and these are expressed in miles per hour. The two different units expressed here are time and distance.

If you go to the grocery store and try to purchase some bulk nuts, you might have noticed that the price is a rate based on weight. For example, you might see that peanuts are $3 per 250 grams. Some rates do not contain the word per, as the relationship between two different units is already expressed with a new unit altogether. For example, one "Hertz" equals 1 cycle per second. When we hear the word "Hertz," we already know that there is a relationship between cycles and time. A Hertz is an example of a "unit rate." This is because this rate has been simplified so that it has a denominator of 1. In other words, 1 Hertz = 1 cycle/1 second. We can express rates in a number of ways: • Using units like Hertz • Using fractions • Spelling them out ## Common rates in everyday life Common rates you might have encountered in everyday life include: • Hourly wages ($15 per hour)
• Interest rates (also expressed as a percentage)
• Birth rates
• Speed limits
• Odds (also expressed as ratios)

## Topics related to the Rates

Rate-Time-Distance Problems

Rate of Change

Rates and Ratios