Common Core Alignment

CCSS.Math.Content.1.NBT.5 - Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.

5: Math

Unit 7: Place Value
Lesson 13: 10 More and 10 Less
Lesson 14: Working With Multiples of 10
Lesson 15: More Practice With 10