Which One Doesn’t Belong: First Grade
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 twodigit 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 twodigit 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) 

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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.
Teacher & School Info

Kristin Gray
 School Details
 Shields (Richard A.) Elementary School Lewes, DE
 Population
 722 students
 District Spending
 $14,381
Supporting Materials

Lesson Plan: Which One Doesn't Belong Planning Guide.PDF

Reflection and Resources.PDF