Repeated additionGet 3 of 4 questions to level up!
Basic Subtraction. You can count back to find the difference or use fact families and related facts to subtract. You can also use a fact triangle, a number line, or draw pictures to help you subtract. You'll watch as Annie writes and solves subtraction sentences using numbers, the minus sign, and the equal sign.
Add 1s or 10s (no regrouping)Get 5 of 7 questions to level up!
Subtracting 1s or 10s (no regrouping)Get 5 of 7 questions to level up!
Add 2-digit numbers (no regrouping)Get 5 of 7 questions to level up!
![Algebra Subtraction Hook Algebra Subtraction Hook](/uploads/1/2/4/9/124921619/971597009.gif)
Break apart 2-digit addition problemsGet 3 of 4 questions to level up!
Regroup when adding 1-digit numbersGet 5 of 7 questions to level up!
Subtract 2-digit numbers (no regrouping)Get 5 of 7 questions to level up!
Subtract 1-digit numbers with regroupingGet 5 of 7 questions to level up!
Add 2-digit numbers by making tensGet 3 of 4 questions to level up!
Add 2-digit numbers by making tens 2Get 3 of 4 questions to level up!
Select strategies for adding within 100Get 5 of 7 questions to level up!
Add and subtract using a number lineGet 3 of 4 questions to level up!
Subtract within 100Get 5 of 7 questions to level up!
Add and subtract on the number line word problemsGet 5 of 7 questions to level up!
Add and subtract within 100 word problems 1Get 5 of 7 questions to level up!
Add and subtract within 100 word problems 2Get 5 of 7 questions to level up!
Add and subtract within 100 word problems 3Get 5 of 7 questions to level up!
Challenging add and subtract word problems (within 100)Get 5 of 7 questions to level up!
Skip-count by 10sGet 5 of 7 questions to level up!
Skip-counting by 100sGet 5 of 7 questions to level up!
Find the missing number (add and subtract within 100)Get 3 of 4 questions to level up!
About this unit
Learn to add and subtract two-digit numbers within 100.The basics of algebra involve symbols. Algebra uses symbols for quantities, operations, relations, or grouping. The symbols are shorthand and are much more efficient than writing out the words or meanings. But you need to know what the symbols represent, and the following list shares some of that info.
- Addition (+): This symbol means add or find the sum, more than, or increased by; the result of addition is the sum.1 + 2 = 3
- Subtraction (–): This symbol means subtract, minus, or decreased by or less; the result is the difference.3 – 2 = 1
- Multiplication (×, ∙, *): These symbols all mean multiply or times. The values being multiplied together are the multipliers or factors (in this example, 2 and 3), and the result is the product (in this example, 6). You’ll see the dot (∙) more often than the times symbol (×) because the dot is easier to write and the times symbol can be confused with the variable x.
- Division (÷, −, /): The division, fraction line, and slash symbols all mean divide. The number to the left of the ÷ or / sign or the number on top of the fraction is the dividend (in this example, 6). The number to the right of the ÷ or / sign or the number on the bottom of the fraction is the divisor (in this example, 2). The result is the quotient (in this example, 3).
- Radical (√): This symbol means to take the square root of something — to find the number which, multiplied by itself, gives you the number under the sign. Here’s an example:
- Absolute Value (| |): This symbol means to find the absolute value of the number between the two vertical lines, which is the number itself or its distance from zero on the number line. Absolute values are always positive. Here’s an example:
- Ellipsis (…): This symbol means et cetera, and so on, or in the same pattern. You use an ellipsis in algebra when you have a long list of numbers and don’t want to have to write all of them.
- Pi (Π): The Greek letter pi refers to the irrational number, 3.14159…. Pi represents the relationship between the diameter and circumference of a circle.