# Which One Doesn’t Belong: First Grade

Grade 1 / Math / Tch DIY
CCSS: Math.1.NBT.B.2a Math.1.NBT.B.2b

Common Core State Standards

 Math Math 1 Grade 1 NBT Number & Operations in Base Ten B Understand place value 2a Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases: a. 10 can be thought of as a bundle of ten ones -- called a "ten." b. The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones. c. The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones). Download Common Core State Standards (PDF 1.2 MB)

Common Core State Standards

 Math Math 1 Grade 1 NBT Number & Operations in Base Ten B Understand place value 2b Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases: a. 10 can be thought of as a bundle of ten ones -- called a "ten." b. The numbers from 11 to 19 are composed of a ten and one, two, three, four, five, six, seven, eight, or nine ones. c. The numbers 10, 20, 30, 40, 50, 60, 70, 80, 90 refer to one, two, three, four, five, six, seven, eight, or nine tens (and 0 ones). Download Common Core State Standards (PDF 1.2 MB)

A "Which One Doesn't Belong" routine encourages students to reason about the similarities and differences among a set of numbers, expressions, shapes, or images.

Tch visited Kristin's Gray's school. Watch the video.

Common Core Standards
Math.1.NBT.B.2a, Math.1.NBT.B.2b