Activity 13.1
Ten-Frame Adding and Subtracting

  Review the make-ten idea (add on to get up to 10 and then add the
 rest) using two ten-frames. Use single digits to start and then progress
 to two digit numbers. Two students work together. First, they
 make a specified two digit number with the little ten-frames cards.
 They then stack up all the less-than-ten cards and turn them over one
 at a time. Together they talk about how to get the total quickly.

 The same approach is used for subtraction. With 53 - 7, take off 3
 to get to 50, and then 4 more to get to 46.

Activity 13.2
Numbers, Squares, Sticks, and Dots

Prepare a worksheet or overhead transparency on which a numeral
and some base ten pieces are shown. Use small squares, sticks,
and dots for base ten pieces to keep the drawing simple.
Students write the totals that they compute mentally.

     Example:

                           
                       •••   |||      equals   66
                       •••

Activity 13.3
50 and Some More

Say a number between 50 and 100.
Students respond with "50 and _____."
For 63, the response is 50 and 13.
Use other numbers that end in 50 such as "450 and some more."
 

Activity 13.4
The Other Part of 100

 Two students work together with a set of little ten-frame cards. One
 student makes a two-digit-number. Then both students work mentally
 to determine what goes with the ten-frame amount to make 100. They
 write their solutions on paper and then check by making the other part
 with the cards to see if the total is 100. Students take turns making
 the original number.
 If the original number is 28, then thought processes include:
     Two more makes 30 - 70more is 100 - so 72
     28 and 70 is 98  and 2 makes 100 - so 72
     80 is too much so it has to be 70-something and
        2 goes with the 8
 

Activity 13.5
Compatible Pairs

  Searching for compatible pairs can be done as a worksheet activity or
  with the full class using the overhead projector. Prepare a transparency,
  or duplicate a page, with a search task (see below). Students call out
  or connect the compatible pairs as they see them.


      Make 10                         Use 5 to make 100


                               

Activity 13.6
Calculator Challenge Counting

  Students press any number on a calculator (like 17) and the + 8.They
  say the sum before they press =. Then they continue to add 8 mentally,
  challenging themselves to say the number before they press =.
  They see how far they can go before making a mistake.

Activity 13.7
Little Ten-Frame Addition and Subtraction

Provide a set of little ten-frame cards for each of two students. Each
student makes a number with her/his cards. When both have their
number ready, they place it out so both can see. Then they try to be
the first to tell the total.

For the subtraction version, one student makes a number greater
than 50 and the other writes a number on paper that is less than 50.
The written number is to be subtracted from the modeled number.
Students should be encouraged to share strategies to see how fast
they get.