Download W-L Ch.13, 3,4,5

Denise Lenihan
10/13/12
Mathematics
W-L Ch. 13 p. 256 #3,4,5
3. The one division concept that is easier for direct modeling and for developing the
standard long-division algorithm is the fair-share, partitioning concept. After time,
however, students will learn to solve both types of problems. An example word
problem for 735 divided by 6 is, there are seven hundred, thirty-five candy bars in a
bowl outside the door for trick-or-treaters. If six kids come up and they split the
candy evenly, how many candy bars will each kid get?
4. The standard algorithm for 735 divided by 6 would be:
And then to repeat the process using the text’s suggestion of recording trades
explicitly:
5. Estimation Strategies
A. Front-End: The front-end method uses the leftmost digits only and covers
up all the other digits. For example, in a multiplication problem, 37 x 55, students
consider just the 3, 30 and the 5, times 50, which would be 1500.
B. Rounding: Rounding changes the numbers in the problem to others that
are easier to compute mentally, it is flexible and most familiar. For example, in a
multiplication problem, 5 x 73, 73 is estimated to 70, therefore 5 x 70 is 350, thus 5
x 73 is a little above 350, around 360.
C. Compatibles: Most used in division, the divisor or dividend is adjusted to
close numbers that result in whole numbers to make mental math easier. For
example, compatibles are often used with fractions or decimals, such that a carton of
a dozen eggs cost a total of $2.65, how much is each egg. 12 eggs times 20 cents per
egg would be $2.40, approximately close to $2.65.
D. Adapting to use tens, hundreds, and so forth: In this method, any number
can be changed to make the multiplication or division problem easier by tens,
hundreds, and thousands. For example, 400 x 5, whereby 5 is 10 divided by two,
therefore 400 x 10 is 4000, then take half of that is 2000.