2.NBT.6/NUMBERS AND OPERATIONS IN BASE TEN



MATH DOMAINAugust 20132.NBT.6/NUMBERS AND OPERATIONS IN BASE TENGrade 2Math ClusterMath StandardMathematic PracticesUse place value understanding and properties of operations to add and subtract.2.NBT.6 Add up to four two-digit numbers using strategies based on place value and properties of operations.Make sense of problems and persevere in solving them.Reason abstractly and quantitatively.Construct viable arguments and critique the reasoning of others.Model with mathematics.Use appropriate tools strategically.Attend to precision.Look for and make use of structure. Look for and express regularity in repeated reasoning.Reporting StandardTrimester 1Trimester 2Trimester 3Base Ten: Add any two- and three-digit numbers.Base Ten: Subtract any two- and three-digit numbers.Add four one-digit numbers without composing(not tested)Introduced (not tested)Add up to four two-digit numbers without composing(tested)Clarify StandardMental strategies AND Standard algorithm should be learned.Adding numbers together is composing new numbers.Subtracting and taking numbers apart is decomposing numbers.The terms “composing” and “decomposing” replace “regrouping” and “borrowing” in the CCSS Mathematics.Task Analysis1.NBT.2 Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand:10 can be bundled and call a “ten.”11-19 are composed of a 10 and numeral between 1 and 9 which represent ones.Counting by tens refers to bundles of tens. For example, “20” refers to two bundles of ten.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.Learning Tasks:Mental strategies can be effective when dealing with equations (sideways problems).Understand that when adding or subtracting multiple-digit numbers, like units are added or subtracted together (hundreds + hundreds, tens + tens)Strategy: Add ones and tens separately and then combine: 13 + 25 + 42 + 58 13 + 25 + 42 + 58 10 + 20 + 40 + 50=120 OR 3 + 5 + 2 + 8 =18 3 + 5 + 2 + 8 = 18 10 + 20+ 40 + 50 = 120 120 + 18 = 138 120 + 18 = 138An “up-and-down” addition or subtraction computation problem is called an algorithm.In order to ensure consistency across the elementary schools in Auburn SD, second graders need to learn what is called “the standard algorithms” for two- and three-digit addition and subtraction.Here is one way to teach the standard algorithm for addition. By the end of 2nd grade students can transition to putting the “1” at the top of the appropriate column.2.NBT.6 Add up to four two-digit numbers using strategies based on place value and properties of operations.VocabularyPrior Explicit ComposeMaking tensHundredsTensOnes2NBT.6 Sample Assessment Items earning a “3” in the reporting system??56 + 18 + 65 = _______ 87 + 16 + 23 + 30=________ 34 67 27 33 13 + 15 + 362.NBT.6 Sample Assessment Items earning a “3” in the reporting systemType of Whale Length in Feet at BirthGray whale baby14Blue whale baby23Minke whale baby9Right whale baby20Bob was doing a science project on how long 4 different kind whales are when they are born. He needed butcher paper cut to the exact length for each baby whale. His teacher sent him to the office to get the paper. Bob wanted to get just one long piece of butcher paper and then cut the paper into exact lengths for each baby whale. When Bob asks the office for the exact length of paper, how long should the paper be?Assessment Rubric1No evidence of a strategy.2Evidence that the student used a correct strategy but answered incorrectly. OR The student answered correctly with no evidence of strategy.3 Evidence that the student used a correct strategy, and correct equation, and answered correctly.4On a level 4 question: Evidence that the student used a correct strategy, and correct equation, and answered correctly.1.NBT.6 Sample Assessment Items earning a “4” in the reporting systemType of Whale Weight in Pounds at BirthGray whale baby2,000Blue whale baby?Minke whale baby1,000Fin whale?A Blue whale baby is usually 3 times heavier than a gray whale baby when it is born. A Fin whale baby weighs 2,000 pounds less than a blue whale at birth.Most mother whales give birth to one or sometimes two babies. The interesting fact about Fin whales is that they give birth to up to 6 babies at a time. Suppose 6 babies all weighed the same as in the data chart.How much would 6 Fin whale babies weigh at birth according to the chart? ................
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