Forming expressions

Task goals

• Use a letter to represent an unknown quantity, and explain what that variable stands for in a real-world context.
• Translate a word sentence into an algebraic expression, using brackets or a fraction bar to show the intended order of operations, e.g. "3 more than two sevenths of a number" becomes $\dfrac{2}{7}x+3$.
• Form an expression for a total cost, age, or measurement from a described situation, e.g. a $\$5$ base charge plus $\$3$ per kilometre $k$.
• Form and simplify an expression for the perimeter or area of a shape whose side lengths are given as variables.
• Form an expression that includes a fraction, a percentage increase, or an irrational number such as $\pi$.
• Distinguish an expression from an equation, and explain why an expression cannot be "solved" the way an equation can.