An equation is a way to say that 2 things are equal, using an equal sign =.
This is an equation:
12 + 10 = 22
The equal sign = in an equation tells you that the left side is equal to the right side.
Sometimes there's a part in an equation that is not known.
For example:
2 + 9 = ?
The value on the right is not known. So we write a question mark for it.
But instead of writing a question mark (?) for the missing part, we can represent the unknown number by a letter.
2 + 9 = s
A letter used to represent an unknown number is called a variable.
Tip: You can use any letter in the alphabet as a variable.
Tip: to vary means to change. So a variable is something that can change its value, unlike a number which always has itself as the value. 1 is always just 1!
What's the variable in our equation above?
The variable is 's'.
Did you notice that an equation always has two sides?
Each side is called an expression.
An expression is made up of either a variable, a number, or a combination of numbers, variables, and operations like + or -.
Look at this equation:
z = 3 + 4
The expression on the left is the variable x.
The expression on the right is "3 + 4".
Check out this expression:
p - 6
What is the value of this expression if p is equal to 10?
Let's replace p with 10.
10 - 6
Now we can simplify it.
10 - 6 = 4
So when p equals 10, the value of the expression p - 6 is 4.
Let's try to solve some equations with variables.
Solve for 's' in this equation.
2 + 9 = s
Tip: when math people say "solve for s", it's a shortcut for saying "find the value of s that keeps the equation balanced, or true."
How do we solve for 's' here? 🤔
We simplify the left side.
2 + 9 = s
11 = s
The value of the variable s is 11 in this equation.
Great job.
Solve for 'r' in this equation.
r = 18 - 9
We just need to simplify!
r = 18 - 9 = 9
So the value of the variable r is 9.
r = 9
Excellent work. 👏
Now, complete the practice. You'll learn more and remember for longer.