CCSS 1.NBT.5 Worksheets

CCSS 1.NBT.5 (Common Core, 1st Grade): "Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used." The worksheets below practice this standard. Each one is a free printable PDF with an answer key, comes in multiple versions, and can also be assigned digitally - no login or account needed.