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Chapter 4.5, Problem 8P

AThe exchanges that follow are taken from Developing Children ‘s Understanding of the Rational Numbers: A New Model and an Experimental Curriculum by Joan Moss and Robbie Case [53, p. 135]. “Experimental Si” and “Experimental S3” are two of the fourth-grade students who participated in an experimental curriculum described in the article.*

*From Journal for Research in Mathematics Education, Vol. 30, No. 2, 122—147 by Robbie Case and Joan Moss. Copyright© 1999 by National Council for Teachers of Mathematics (NCTM). Used by permission of National Council for Teachers of Mathematics (NCTM).

Experimenter: What is 65% of 160?

Experimental S1: Fifty percent (of 160) is 80. I figure 10%, which would be 16. Then I divided by 2, which is 8 (5%) then 16 plus 8 um.. . 24. Then I do 80 plus 24, which would be 104.

For each of the two students’ responses, write strings of equations that correspond to the student’s method for calculating 65% of 160. State which properties of arithmetic were used and where. (Be specific.)

Write your string of equations in the following form:

   65 %   .   160   =   s o m e   e x p r e s s i o n = . : =   s o m e   e x p r e s s i o n

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Chapter 4 Solutions

Mathematics for Elementary Teachers with Activities, Loose-Leaf Version Plus MyLab Math -- Access Card Package (5th Edition)

Ch. 4.2 - Mary says that 103.7=3.70. Why might Mary think...Ch. 4.2 - Now that you understand why multiplying a number...Ch. 4.2 - a. Find the decimal representation of 137 to at...Ch. 4.2 - Find the decimal representation of 141 to at least...Ch. 4.3 - There are 31 envelopes with 3 stickers in each...Ch. 4.3 - Here is Amy’s explanation for why the commutative...Ch. 4.3 - Using the definition of multiplication, explain...Ch. 4.3 - Use the definition of multiplication to explain...Ch. 4.3 - Figure A in Figure 4.21 I shows a 5-unit- high,...Ch. 4.3 - Write three different expressions for the total...Ch. 4.3 - Suppose you have 60 pennies arranged into 12...Ch. 4.3 - To calculate 3.80 mentally, we can just calculate...Ch. 4.3 - Write equations to show how the commutative and...Ch. 4.3 - Explain how to use the associative property of...Ch. 4.3 - Use the associative property of multiplication to...Ch. 4.3 - Explain how to make the following product easy to...Ch. 4.3 - Julia says that it’s easy to multiply a number by...Ch. 4.3 - Carmen says that it’s easy to multiply even...Ch. 4.3 - The Browns need new carpet for a room with a...Ch. 4.3 - If a roll of a certain kind of wrapping paper is...Ch. 4.3 - Ms. Dunn’s class wants to estimate the number of...Ch. 4.3 - Imagine that you are standing on a sandy beach,...Ch. 4.3 - A lot of gumballs are in a glass container. The...Ch. 4.3 - Figure 4.27 shows a grocery store display of cases...Ch. 4.3 - Use the facts that 1mile=1760yards 1yard=3feet...Ch. 4.3 - A roll of wrapping paper is 30 inches wide. When...Ch. 4.3 - Estimate how many neatly stacked hundred-dollar...Ch. 4.3 - * A cube that is 10 inches wide, 10 inches long,...Ch. 4.3 - * Investigate the following two questions, and...Ch. 4.3 - * The Better Baking Company is introducing a new...Ch. 4.4 - Ben and Charles are working on 4+3.2.10 Ben says...Ch. 4.4 - a. There are 6 cars traveling together. Each car...Ch. 4.4 - The students in Mrs. Black’s class are arranged as...Ch. 4.4 - Describe one collection of things whose total...Ch. 4.4 - There are 6 cars traveling together. Each car has...Ch. 4.4 - Draw arrays to help you explain why the equations...Ch. 4.4 - Explain how to use the distributive property to...Ch. 4.4 - Explain how to calculate 29 .20 mentally by using...Ch. 4.4 - Ted thinks that because 10.10=100and2.5=10, he...Ch. 4.4 - Working on the multiplication problem 21. 34,...Ch. 4.4 - Use the distributive property several times to...Ch. 4.4 - In Section 4.2, we drew pictures of bundled...Ch. 4.4 - *a. Use an ordinary calculator to calculate 666,...Ch. 4.4 - * Without using a calculator or computer and...Ch. 4.4 - * Check the following:...Ch. 4.4 - Determine which of the following two numbers is...Ch. 4.4 - * The square of a number is just the number times...Ch. 4.4 - * The square of a number is just the number times...Ch. 4.5 - Josh consistently remembers that 77=49 , but he...Ch. 4.5 - Demarcus knows his 1,2,and3 multiplication tables....Ch. 4.5 - Suppose that a student has learned the following...Ch. 4.5 - For each of the multiplication problems (a)...Ch. 4.5 - Suppose that the sales tax where you live is 6%....Ch. 4.5 - Clint and Sue went out to dinner and had a nice...Ch. 4.5 - Your favorite store is having a 10%-off sale,...Ch. 4.5 - AThe exchanges that follow are taken from...Ch. 4.5 - Here is Marco’s method for calculating 38 60: Four...Ch. 4.5 - Jenny uses the following method to find 28% of...Ch. 4.5 - Use properties of arithmetic to calculate 35% of...Ch. 4.5 - Use the distributive property to make it easy for...Ch. 4.5 - Tamar calculated 41 41 as follows: Four 4s is 16,...Ch. 4.5 - Here is how Nya solved the problem 34.72: Half of...Ch. 4.5 - a. Lindsay calculates two-fifths of 1260 by using...Ch. 4.5 - While working on the multiplication problem 38 ....Ch. 4.5 - There is an interesting mental technique for...Ch. 4.5 - * Try out this next mathematical magic trick. Do...Ch. 4.6 - Solve the multiplication problem 896_ in three...Ch. 4.6 - Solve the multiplication problem 7684_ in three...Ch. 4.6 - Solve the multiplication problem 43237_ in three...Ch. 4.6 - When we multiply 2637_ by using the common method,...Ch. 4.6 - a. Use the partial-products method to calculate...Ch. 4.6 - a. Use the partial-products method to calculate...Ch. 4.6 - a. Use the partial-products and common methods to...Ch. 4.6 - a. Draw an array on graph paper, and use your...Ch. 4.6 - Solve the multiplication problem 2327 by writing...Ch. 4.6 - a. Use the partial-products and common methods to...Ch. 4.6 - a. Use the common method to calculate 2437 b. On...Ch. 4.6 - The lattice method is a technique that is...Ch. 4.6 - The following method for multiplying 2123 relies...

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