Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
Number and Quantity
Number & Operations in Base Ten: Use place value understanding and properties of operations to add and subtract.
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Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
Number & Operations in Base Ten: Perform operations with multi-digit whole numbers and with decimals to hundredths.
Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
Add and subtract within 1000, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method. Understand that in adding or subtracting three-digit numbers, one adds or subtracts hundreds and hundreds, tens and tens, ones and ones; and sometimes it is necessary to compose or decompose tens or hundreds.
Mentally add 10 or 100 to a given number 100-900, and mentally subtract 10 or 100 from a given number 100-900.
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
Mentally add or subtract 10 to or from a given two-digit number. Explain the reasoning used.
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
