Subtraction and Regrouping

The following site gives a great illustrated and animated explanation for regrouping when subtracting.
http://www.mathsisfun.com/numbers/subtraction-regrouping.html

Another topic we have been working on is subtracting across zero. Most students have surprisingly done very well with this skill - it is usually pretty challenging!

Click on the link below and scroll down to find a tutorial, sample games and a quiz to check your child's understanding or mastery.
http://www.macmillanmh.com/math/2009/ca/student/grade3/chapter_03.html

Virtual Base Ten Pieces

This site might be helpful if your child is struggling with the concept of "regrouping" in addition.

VIRTUAL BASE TEN PIECES
http://olc.spsd.sk.ca/de/math1-3/baseten-1.html

Addition

Most students are doing a great job with addition, but some tips for helping your child are included below:

Multi-digit addition can be a challenging concept for some. In order to help students, remind them that they need to -

1) LINE UP DIGITS. Many students are forgetting to line up their digits so that the ones place is directly over the ones place in the addend

368
+219
_____

The 8 and the 9 are directly over each other, helping the child to clearly see what needs to be added together (and to make sure they are adding the correct digits).

2) ADD THE ONES COLUMN FIRST. After adding the ones column, proceed by adding the tens, then the hundreds, etc. Multi-digit addition should always be done RIGHT to LEFT.

3) If, when adding a column together, the sum is larger than 9, students will have to REGROUP. See example below:

278
+159
_____

8+9 is larger than 9, so 17 has to be regrouped as 1 ten and 7 ones. Students should write down the 7 in the ones place and "carry" the one over to the tens. We have practiced using base-ten pieces in class, so students should be able to visualize, or draw out a visual representation of "17" using base ten pieces.

4) ADD ALL DIGITS in a column - even the "carried" digits.

5) CHECK WORK....does it make sense? Often, students will record a sum that is SMALLER than the addends they began with. This is just a careless error and can be easily fixed if students check, or proof their work.

ROUNDING

Rounding is a math concept that is sometimes tricky for students. Some students will master the concept with ease, while others are often stumped by its more abstract nature. I encourage my students to think about rounding in conjunction with a roller coaster or a hill with a car. Numbers either roll over the hill (rounding up) or fall back down the hill (rounding down). The trick is to teach students to look, like a detective, at the CLUE the number leaves for you. This clue is the digit to the RIGHT of whatever place you are rounding to. For example:

Round 62 to the nearest TEN.

Look at the TENS place (6, value 60)

Look at the digit to the right of the tens place, in the ones place (2)

If the number to the right of the place being rounded is 5 or GREATER, round the number up. If the number is less than 5, round DOWN.

I ask students to always lay out two possibilities or choices. See the example below:

45 - round to the nearest ten

Choices: 40 or 50 (since rounding to the nearest ten, my choices must end in zeros)

Look at the tens place (4, value 40)

Look at the ones place - the digit is 5, therefore I will round up

The answer is 50

It often helps students to have a visual of a hill and even a paper car to move up and down the hill. The important steps to remember:

1) Think through both choices (rounding up or down)

2) Look at the place you are asked to round to

3) Look at the secret number to the RIGHT of the place you are rounding to

4) Decide if you should round UP or DOWN

I will post a video later in the week.

MATH UPDATE

We have been working hard on place value - all the way to the ten thousands place! I have been so impressed at the number sense my students already have demonstrated. Very refreshing and encouraging! The next logical skill to work on in the world of number sense is comparing and ordering numbers. Today we worked on greater than and less than. We discussed comparing simple, 1-digit numbers, all the way to 4 and 5-digit numbers! We enjoyed some hands-on game activities in small groups, discussed real life applications (comparing items when shopping), enjoyed a fun song/visual representation of comparing numbers (stay tuned for a video clip) and then practiced through written notation using <, >, and =.

TIP: When helping students compare numbers with multiple digits, always compare each place value, one at a time. Also, always start with the LARGEST place.....not the ones place.

For example:

5, 679 ____ 5, 782

Compare the 5's first (thousands place)

Then compare the hundreds (6 vs. 7)

Students should know that 7 is greater than 6, so 5,782 is GREATER than 5,679.

MATH CURSE

Today we read the book, Math Curse, which gave us a wonderful introduction to our math curriculum for the school year. If you have never seen the book, you should definitely check it out! In the book, a female student is told by her teacher that "you can think of everything as a math problem." Sure enough, the next day, she wakes up and experiences math through every facet of her daily life! I used this book as a springboard as we discussed ways we use math in our everyday lives....with the recurring theme being "we cannot escape math!" We solved some of the girl's "math curse problems" together as a class, and then students demonstrated their own mathematical skills by solving problems individually (applying addition, subtraction, counting by 2's, 10's or repeated addition, and fractions).