This gives students a chance to notice duplicates, sort the cards into categories, and begin to search for patterns. Neither a 1 nor a 2 can be the hundreds digit of the answer. The digits in the answers add up to 18. Have students record in their journals the patterns they observed in the solutions. Have students record in their journals a conjecture that was proven false with a counterexample, along with the counterexample that was used.
Students can explore how to change the problem to involve subtraction instead of addition.
Students can explore how to change the problem to include the digit 0.