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Welcome! Today we are going to explore how math uses secret code words called variables to solve everyday mysteries.
In math, a variable is just a letter (like x, y, or n) that stands in for an unknown number. Think of it like an empty mystery box waiting to be filled with a value!
An expression is a mathematical phrase that combines numbers, operation signs, and variables. For example, if we have a box of mystery markers and add 3 more, we can write that as 'x + 3'.
When we find out what number the variable represents, we can 'evaluate' the expression. This just means we plug the real number into our mystery box and do the math!
✏️ Worked example
Evaluate the expression 4y - 2 when y = 6.
- Identify the variable and its value. Here, the variable is y, and we are told y = 6.
- Replace the variable y with the number 6. Remember, '4y' means 4 multiplied by y. So, it becomes 4 * 6 - 2.
- Follow the order of operations (PEMDAS). Do the multiplication first: 4 * 6 = 24.
- Finally, do the subtraction: 24 - 2 = 22.
- The evaluated value of the expression is 22!
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