Studyfin
✨ Sign up free
Hey there! Today we are going to unlock a math superpower: using mystery boxes to solve puzzles!
In math, a variable is just a letter (like x or y) that stands in for a mystery number. Think of it like an empty gift box waiting to be filled with a surprise value!
When we combine numbers, operations (+, -, *, /), and variables together, we get an expression. For example, 'x + 3' means whatever mystery number is in our box, we just add 3 to it!
We can evaluate an expression by replacing the variable with a real number. Watch how the expression 'x + 3' changes its total value when we slide a 5 into the mystery box!
✏️ Worked example
Evaluate the expression 'y - 4' when y = 10.
- Identify the variable in the expression, which is 'y'.
- Look at the given value for the variable: we are told that y = 10.
- Replace the letter 'y' in the expression with the number 10. The expression 'y - 4' becomes '10 - 4'.
- Subtract 4 from 10 to get your final answer: 6!
Want the full interactive lesson — quiz, animations, and Finn cheering them on?