Solve rate and unit-conversion problems.

Imagine you are texting a friend in another country about the weather. You say it is 75 degrees outside, but they use Celsius, not Fahrenheit. Without converting the units, your friend has no idea whether to wear a jacket or shorts! Unit conversion (changing a measurement from one unit to another) has been important for thousands of years.

Ancient traders needed to compare weights and lengths across different kingdoms. A rate (a ratio that compares two quantities with different units, like miles per hour) also became essential as people traveled and traded goods. Let's look at how these ideas developed.

On the ISEE, you will see problems that ask you to convert between units and use rates to find answers. The good news is that a simple, repeatable method works every time. Let's learn it!

Before we start solving problems, you need to understand four key ideas. These are the building blocks for every rate and conversion problem you will see on the ISEE.

The diagram below shows how unit conversion works step by step. You start with the value you are given, multiply by a conversion factor, cancel matching units, and arrive at your answer in the new unit.

Notice that the unit "ft" appears once on top and once on bottom. Those two cancel, leaving only "in" as the unit. This is the most important trick for unit conversion: set up the fraction so the unit you want to get rid of cancels out.

There are only a few formulas you need for rate and conversion problems on the ISEE. Let's learn each one.

The ISEE will give you the conversion factor if it is unusual, but you are expected to know everyday ones. The table below lists the most commonly tested conversions. You don't need to memorize all of them — but the highlighted ones appear very often.

To convert in the metric system, count how many steps you move on the staircase. If you go down 3 steps (kilo to base), move the decimal 3 places to the right. If you go up 2 steps (base to hecto), move the decimal 2 places to the left.

Let's solve a typical ISEE-style rate problem from start to finish. Follow each step carefully — this is the exact process you should use on test day.

Knowing the math is only half the battle. You also need smart test-taking strategies. Here are the most common mistakes students make on rate and conversion problems — and how to avoid them.

Once you master single-step conversions, you might see problems that require two or more conversions chained together. For example, converting miles per hour to feet per second requires changing both the distance unit AND the time unit.

Don't worry about the advanced level right now. For the ISEE Middle Level, sticking with the four-step process you learned in Section 3 will handle every problem. As you move into higher-level math and science, you will chain more conversion factors together — but the method is exactly the same!

Now it is your turn! Try each problem before looking at the answer. Remember: on the ISEE, there is no penalty for guessing, so always pick an answer. Use process of elimination to get rid of choices that cannot be right.