1.NR.5.2
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
Khan Academy ResourcesSubtract within 100 using place value blocksAdd within 100 using place value blocksAdd within 100 using a number lineAdding up to four 2-digit numbersSelect strategies for adding within 100Break apart 2-digit addition problemsSubtract within 100 using a number lineAdd 2-digit numbers by making tensAdding by making a group of 10Missing numbers in addition and subtractionAddition and subtraction with number linesAdding 2-digit numbers without regroupingSubtracting 1s using place valueSubtracting a 1-digit number with regroupingSubtracting 10s using place valueUnderstanding place value when adding onesStrategies for adding 2-digit numbersSubtracting two-digit numbers without regroupingAdding with regroupingUnderstanding place value when adding tensBreaking apart 2-digit addition problemsAdding 53+17 by making a group of 10
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