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Through regular experiences with mental math children come to realize
that many calculations are in fact easier to perform mentally. In
addition, when using mental math children almost always use a method
which they understand (unlike with written computation) and are
encouraged to think actively about relationships involving the
particular numbers they are dealing with.
In order to be effective Mental Math sessions should:
Following are some possible activities for K5 classrooms:
Fill the Hundreds Chart:
On day one display a Hundreds Pocket Chart
with only 56 pockets filled with the correct numerals. Leave all other
pockets blank. Select 3 numerals and 3 students. Ask each student to
place his/her numeral in its correct pocket and to explain the strategy
they used to help them complete this task. Repeat the above with 3
numbers and 3 students per day until all pockets are filled.
Take note of students who use a count by one strategy and those who
demonstrate an awareness of the base ten patterns underlying the chart. Select numbers based on your knowledge of individual student’s number
sense (e.g. you may select a number immediately before or after a number
that is already on the board for one child and a number that is 10 or
11 more than a placed number for another child who you feel has a good
understanding of the base ten pattern).
Possible questions to involve other students:
Yesterday we had __ numbers on our number chart and today we added 3
more. How many numbers do we now have on our number chart? How do you
know?
If there are __ numbers on our number chart how many more numbers do we
need to add to fill our chart? Ask several students to explain the
strategy used to solve this problem.
We now have ____ numbers on our number chart. If we continue to add 3
numbers every day how many more days/weeks will it take to fill our
number chart? Explain your thinking.
Today’s Number is…
Select a number for the day (e.g. 8) and write it on the board or chart
paper. Ask students to suggest calculations for which the number is the
answer. Write students' suggestions in 4 columns (addition examples,
subtraction, multiplication and division). After 8 or 10 responses,
focus in on particular columns or types of responses that you would like
more of. For example,"Give me some more addition examples", "Give me
some ways which use three numbers", "Give me an example using
parentheses" etc.
What's My Number
Select a number between 1 and 100 and write it down without revealing it
to your students. Have students take turns to ask questions to which
you can only answer ‘yes’ or ‘no’.
Record each question and answer on chart paper. For example:
Is it greater than 30? No
Is it an even number? Yes
Is it a multiple of 3? No
Does it have a 4 in the ones place?...
After 3 or 4 questions ask, “What is the smallest number it could still
be? What is the largest? Discuss why it is better to ask a question such
as "Is it an odd number?" than "Is it 34?" early in the game. To ensure
that all students are involved have them use individual laminated 100
charts with dry erase markers to mark off numbers after each question is
asked. Keep going until the number has been named correctly. During the
game you may also want to keep track of how many questions are asked
before the number is named. Next time you play challenge students to
guess the number with fewer questions.
'Friendly' number activities
Give a number less than 10. Students must respond with an addition fact
that will make the number up to 10. For example, if today's target
number is 10 and you say 6 the student must respond with "6 + 4 = 10".
Vary the target number e.g. 20, 50, 100, 200, 1000 etc. to suit
students' ability level.