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Math

Arithmetic and pre-algebra

The first math topic. Start here if you want to learn the basics (or just want to make sure you know these topics). After this, you should be ready for algebra. This topic includes videos from the former developmental math playlists.
Community Questions
A thumbnail for: Addition and subtraction
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Addition and subtraction

Adding and subtracting positive and negative whole numbers. Starts with 1+1=2 and covers carrying, borrowing, and word problems.
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Multiplication and division

Multiplying and dividing positive and negative whole numbers, understanding place value, and rounding numbers.
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Factors and multiples

Understanding and finding factors and multiples. After these videos, you'll be ready for fractions.
A thumbnail for: Negative numbers and absolute value
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Negative numbers and absolute value

Extending our understanding of numbers below 0. Thinking about "absolute" distance from 0.
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Decimals

Understanding decimals conceptually, using operations with decimals, rounding and estimating with decimals, and converting decimals.
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Fractions

Understanding fractions conceptually, using operations with fractions, and converting fractions.
A thumbnail for: Ratios, proportions, units and rates
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Ratios, proportions, units and rates

A thumbnail for: Applying mathematical reasoning
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Applying mathematical reasoning

You already have many tools in your mathematical toolkit. In this topic, you'll use these in settings that you're likely to encounter in the real world!
A thumbnail for: Exponents, radicals, and scientific notation
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Exponents, radicals, and scientific notation

Understanding and solving exponents without algebra.
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Arithmetic properties

This tutorial will help us make sure we can go deep on arithmetic. We'll explore various ways to represent whole numbers, place value, order of operations, rounding and various other properties of arithmetic.
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Telling time

Learn to tell time with some fun exercises!
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Measurement

From length to area to volume to time, thinking about how we measure things.
Addition and subtraction
Adding and subtracting positive and negative whole numbers. Starts with 1+1=2 and covers carrying, borrowing, and word problems.

Intro to addition and subtraction

Adding and subtracting is the basis of all mathematics. This tutorial introduces you to one-digit addition and subtraction. You might become pretty familiar with the number line too!

Two digit addition and subtraction

In this tutorial, we'll start adding and subtracting numbers that have two (yes, two!) digits. We won't be doing any carrying or borrowing (you'll learn what those are shortly) so you can see that adding or subtracting two digit numbers is really just an extension of what you already know.

Addition with carrying

You're somewhat familar with adding, say, 17+12 or 21+32, but what happens for 13+19? Essentially, what happens when I max out the "ones place". In this tutorial, we'll introduce you to the powerful tool of carrying and why it works.

Subtraction with borrowing (regrouping)

You can subtract 21 from 45, but are a bit perplexed trying to subtract 26 from 45 (how do you subtract the 6 in 26 from the 5 in 45). This tutorial is your answer. You'll see that we can essentially "regroup" the value in a number from one place to another to solve your problem. This is also often called borrowing (although it is like "borrowing" sugar from your neighbor in that you never give it back).