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===About the Activities===
====Add 2-Digit Numbers====
Two teaching examples show the addition of two 2-digit multiples of ten and the addition of two 2-digit numbers. Each number is graphically represented and the addition process is illustrated on the screen. In the practice exercises which follow each teaching example the digits of the sum must be entered.
[[File:AddSub3 - 2DigitAdd.png|300px|thumb|center|2 Digit Addition]]
====Subtract 2-Digit Numbers====
The teaching example demonstrates the subtraction process used for two 2-digit numbers. No renaming, or borrowing, is necessary. In the practice exercises, each digit of the answer must be entered in subtraction problems which use 2-digit numbers.
[[File:AddSub3 - 2DigitSub.png|300px|thumb|center|2 Digit Subtraction]]
====Regroup Objects====
The first teaching example demonstrates regrouping when there are more than 9 ones, a skill necessary for addition with renaming ("carrying"). The second teaching example demonstrates regrouping one ten to have more ones, a skill which is necessary for subtraction with renaming ("borrowing"). Practice exercises follow each teaching example.\
[[File:AddSub3 - Regroup.png|300px|thumb|center|Regroup Objects]]
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