Mystery Computations

5 min

Narrative

In the next activity, students are asked to look for a rule that puts together some numbers to make a target number. This Warm-up activates that sort of thinking.

Launch

Arrange students in groups of 2.

Ask each student to think of a whole number. (Make this more straightforward by limiting the choices to single-digit numbers, more challenging by limiting to 0–20 or 0–100, or really challenging by placing no restrictions on the numbers.) Select four students at random to share their number, and display these four numbers for all to see.

Student Task

Your teacher will give you 4 numbers. Use these numbers, along with mathematical operations like addition and multiplication, to make 24.

Sample Response

Sample responses:

  • If the 4 shared numbers are 1, 2, 3, and 4. 1234=241 \boldcdot 2 \boldcdot 3 \boldcdot 4 = 24.
  • If the 4 shared numbers are 1, 2, 3, and 5. 23(51)2 \boldcdot 3 \boldcdot (5-1).
  • If the 4 shared numbers are 5, 5, 5, and 5. 5555=245 \boldcdot 5 - \frac55 = 24.
Activity Synthesis (Teacher Notes)

Ask students to share their expression with a partner, so that their partner can verify that their expression is equal to 24. Then, select a few students to share their expression with the whole class and record these for all to see. How many different ways did the class find to make 24?