Subtraction!

We started this week learning about two digit subtraction.  It quickly got tricky as we learned that sometimes we need to "borrow" when there are not enough ones.  When subtracting from a two digit number, follow the steps below:

1) Check to see if you need to borrow. If yes, go to step #2.  If no, go to step #4.
2) Cross out the number in the tens place.  Write the number one less above it.
3) Cross out the number in the ones place.  Write the number ten more above it.  (This is instead of squeezing in a little 1 like we were probably taught)
4) Start in the ones place - subtract.
5) Move to the tens place - subtract.
6) Check your work!  Ask your child how s/he can check the answer to a subtraction problem. (By adding the answer - the difference - to the bottom number of the equation.  That will total the number you were subtracting from.)


Example:

    4  12
    5   2
  - 2   8
     2  4

Think:  I can't subtract 8 from 2, so I need to borrow a 10.  Cross off the 5.  Instead of 5 tens, I now have 4 tens.  Cross off the 2.  Instead of only 2 ones, I now have 12 ones.  (4 tens and 12 ones is the same as 5 tens and 2 ones)  Then I subtract:  12 - 8 = 4.  4 - 2 = 2.
Check!  4+8=12.  2+2=4.  
Done!

Check out papers coming home this week that better illustrate the process.  Don't get tricked! Not all subtraction problems require borrowing.  Also, coming soon are papers with mixed addition and subtraction (with and without regrouping, with and without borrowing).

Addition with Regrouping

We are now moving on to 2-digit addition with regrouping.  Students are directed to continue to add the ones place first.  When that total is 10 or more, they need to mark how many ones below the equation, and how many tens (which it will always be 1) in the tens place above the equation.  For example:

    
        1
        2 7
     + 1 4
            1

Then, students need to add the tens place.  ** Don't forget to add the extra "1" you wrote up above!

       1
       2 7
    + 1 4
        4 1

Look for school work coming home that illustrates the strategy of regrouping.  This may help you to help your child understand the concept of regrouping.

Welcome Back!

We are back from vacation and I am impressed by all the great thinking happening in the room today!  Everybody came back ready to learn!

Here are a few quick updates on what we are learning about:  

Math --  We will continue to visit time and money (telling time to the 5 minutes, identifying coins penny, nickel, dime, quarter, counting coins to a dollar).  We have just started a unit on adding two digit numbers.  We have started with "easy numbers" (no regrouping) to get the feel of how it works.  Students have been taught to stack the numbers (written in vertical formation, lining up the ones and tens places), and to add beginning with the ones place, then moving left on to the tens place.  This is a very important habit to get into, because once we move on to trickier numbers (adding with regrouping), if a student starts in the tens place and moves right, they will get stuck!  Homework has come home to give you a feel for how it's being taught.  Adding with regrouping will be coming soon! (Regrouping is the term used when you add the ones place and the answer is 10 or more, so you need to put a 10 into the tens place --  also known as "carrying".)

Science/Social Studies --  We have several mini-units coming up in science and social studies, including: Water Cycle, Martin Luther King Jr., Constitution and Elections, and President's Day (with a brief biography lesson on Abraham Lincoln and George Washington).