Secret Code Addition with Post Office — Grade 1

This is addition as code-breaking. The letters, stamps and a parcel each carry a hidden value from the legend, and each row strings three or more of them into a sum. The child looks up every picture, writes its number, and adds — practising the several-addend addition that is new at Grade 1. Because the totals never pass twenty, the puzzle stays within reach: a child can always count to confirm the decoded answer.

The substitution step quietly strengthens number sense: a child has to hold what each picture is worth while adding, which is more demanding than reading bare numerals. That is good Grade 1 work, and pairing it with three-or-more-addend sums within twenty builds the comfort with combining several numbers that Grade 1 is meant to develop — without ever leaving the range a child can count to be sure.

Children who like post office treat each row as a small puzzle, which keeps a code-breaker happily adding. When this feels easy, crack the code in secret code addition with reptiles and amphibians, or try secret code addition with toys. You can also browse every secret code addition worksheet or the whole post collection for grade 1 — each sheet prints cleanly or plays online for free.