Third grade students visited Mr. Bulaevsky's website - Base Ten Blocks - and had fun reviewing place value and regrouping in subtraction. I think the hammer is their favorite tool!

Students were given three subtraction problems that require regrouping.

 33-7=? 54-9=? 230-70=?

They moved 3 ten rods into the column for tens. They moved 3 unit blocks into the units column. Since they could not take 7 units away from the units column they had to move or "borrow" a ten rod and place it in the units column. Then they clicked on the hammer and renamed the single ten rod as 10 units. At this point they could take away 7 units from the units column leaving only 6 there. Two ten rods were remaining in the tens column. 33-7=26

For the last problem the students placed 2 hundred blocks or flats in the hundreds column and 3 ten rods in the tens column. They borrowed a hundred block and moved it to the tens column. Then they used the hammer and split the hundred block into 10 ten rods. At this point they had 13 ten rods in the tens column. They lassoed 7 ten rods and moved them to the recycle bin. They had 1 hundred block and 6 ten rods left. In the last picture on the right you can see the lasso holding 7 ten rods on their way to the recycle bin.

 Math presentation prepared by Joyce Perdue and Patti Weeg for the National Title 1 Conference - Tampa, Florida: January 24-26, 2002 | Authors in Residence | Elementary Math Students in the CyberZone | www.globalclassroom.org January 2002