youcubed: What’s the Secret Code?
This task helps students build number sense as they practice calculating.

The task has more than one solution which is nice. At the end it asks students to write a clue that gives the task only one solution.

Task Instructions

  1. Use the clues to find the code number:
    • It is between 8,500 and 8,800.
    • When multiplied by 8, the result is a whole number.
    • The digit in the hundreds place is ¾ the digit in the thousands place.
    • The sum of all digits in the number is 26.
    • The digit in the hundredths place is 200% of the digit in the tenths place.
    • There are no zeros in the decimal places.
  2. What code numbers fit these clues?
  3. Explain how you used all of these clues to find these possibilities.
  4. Write one more clue so that there is only one possible code number.


Paper and Pencils


From Math for All: Differentiating Instruction, Grades 6-8 by Linda Dacey & Karen Gartland (Sausalito, CA: Math Solutions), pp. 257.

Multiplication & Division, Number Values & Counting
Middle School

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youcubed (Stanford University)

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