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"What totals did you get?"
List some of their totals.
"What questions might a mathematician ask now?"
Add to 200 could be used as an activity for students learning to program. They could write a program to find all possible solutions.
For example, this program was written by Nevil Hopley, Head of Mathematics at George Watson's College, for the TI-Nspire software.
If you have the appropriate software, you can download his .tns file here: Add to 200.tns
Having digit cards available for students to physically manipulate will help those who are reluctant to commit ideas to paper.