By discarding standard paper-and-pencil
arithmetic, Marilyn Burns eliminates
about 80% of traditional elementary math education
content. This conveniently
leaves plenty of time for discovery-learning
"problem-solving activities." These time-consuming
activities supposedly
include explorations of advanced topics such as algebra, probability
and statistics. But this is an obvious sham, because math
is a
vertically-structured knowledge
domain. Algebra, probability and statistics are ruled out, if the
student
hasn't first mastered standard paper-and-pencil arithmetic. We're
talking about genuine algebra, probability and statistics, not the
constructivist fuzzy math versions.
Marilyn Burns
"Problem-Solving Activities"
Marilyn Burns promotes "problem
solving as the focus of math teaching." In her book, About
Teaching Mathematics: A K–8 Resource, she offers many examples of
"problem-solving
activities."
- These activities aren't accompanied by a statement of appropriate
grade level, prerequisite math knowledge, or math learning
objectives.
- Although never
explicitly stated, prerequisite math knowledge is often
needed for the Marilyn Burns "problem-solving activities." How
did the child acquire the prerequisite math knowledge needed to solve
the current problem? Constructivists would have you believe
that the child somehow picked up this knowledge while carrying out
earlier "problem-solving activities."
- The Burns problem-solving activities" often consume considerable
time, because they
require extensive busywork and regular use of a wide
variety of "hands-on" concrete objects.
- Example: "Find
all the different ways to arrange four
toothpicks by the
following two rules: 1. Each toothpick must touch the end of at least
one other toothpick. 2. Toothpicks must be placed either end to end or
to make square corners." Page 92
- Question:
What's the point? This question needs to be
asked for every Marilyn Burns "problem-solving
activity."
- Marilyn Burns provides few samples of student
solutions. She regularly states that there are many possible
solutions. But she does offer her solutions to some problems
in Mathematical
Discussions, Part
IV [pages 255 - 308] of About
Teaching Mathematics: A K–8 Resource. Here are four
examples of her solutions:
The X-O
Problem This
problem is given on page 71. The Marilyn Burns solution is found
on pages 266 - 267. Here's a brief statement of the
problem: There are 3 cards in a paper bag: one with an X
on both sides, one with an O on both sides, and one with an X on one
side and an O on the other side. If you draw one of these cards
at
random and look at only one side, how would you predict what is on the
other side? Marilyn
Burns offers her
solution on page 266. She writes "I found choosing a
strategy for this problem perplexing." She then explained that
she first reasoned that there are a total of 3 Xs and 3 Os, so
if she sees an X, then 2 Xs and 3 Os are left. Since there
are more Os left, she will predict the other side will be an
O. More generally, her strategy is to predict the
opposite of what she sees. Marilyn Burns then tested
this strategy by playing 30 games [30 experiments of randomly
drawing 1 of the 3 cards]. She found that her prediction
was
correct less than half the time, so she played another 30
games. Same result. Not satisfied, Marilyn
Burns was then advised by a colleague that she should predict what she
sees, not the opposite. The new logic: "there's a 1/3 chance that
you'll draw a card with an X on one side and an O on the other side,
and a 2/3 chance that you'll draw a card with the same mark on both
sides. A probability of 2/3 is twice as likely as a probability
of 1/3, so predict the mark you see."
Marilyn Burns tested this
new strategy by again playing two rounds of 30 games. This
time she was happy with the results and proclaimed "case closed."
Comment 1: For a mathematically correct
discussion of this problem, see Conditional
Probability. For a more informal discussion and links to
variations , see the Three Cards
Problem.
Comment 2:
Marilyn
Burns appears to believe
that 60 trials proves the correctness of her solution, and her "math"
staff appears to
agree. But an experiment with a small number of
trials [such as 60] may not result in a experimental probability that
is an excellent approximation for the theoretical
probability.
A Tangram Problem
Explain
why it's not possible
to form a square using exactly 6 of the 7 Tangram pieces.
This problem is given on page 83. The Marilyn Burn solution
is discussed on pages 274 - 277. There she discusses how she
formed a panel of 4 Math
Solutions
instructors. They were to help her solve
this
problem.
She writes: "we observed four people rummage for ways to approach the
problem. They cut Tangram pieces; they moved pieces
about; they exchanged ideas; at times, one person would
retreat into private thoughts and then reemerge to share
discoveries." Marilyn Burns later says "I thought about this
problem for a long time - years - before finally making sense of
it for myself." Years!
Comment 1:
Marilyn Burns and her staff spent considerable time trying to "solve"
this problem with a
"hands-on" concrete materials approach. After 3 pages of
discussion, she quietly discards hands-on methods and gives a
traditional solution. The idea is to subtract the area of
the excluded 7th piece from total area of all 7 pieces. This
gives
the area of the potential 6-piece square. Then take the
square root of the 6-piece area to
get the length of the 4 sides of the potential 6-piece square.
Then show that this length
can't be formed using sides of the 6 pieces. Due to congruent
pieces, there are 4 (not 7) cases to consider.
Comment 2: The
successful method requires prerequisite knowledge about area and the
length of sides for squares, triangles, and parallelograms.
This knowledge can't be discovered while the student attempts to
solve this problem.
Squaring Up
Trace around your left foot on centimeter squared paper. Find the area
of your foot. Cut a piece of string so that the length is equal
to the perimeter of your left foot. Tape the string in the form
of a square on centimeter squared paper. How does the area
of your foot compare to the area of the square? This problem is
given on page 54. Marilyn Burns discusses it on page 256.
She writes: "I was mathematically flabbergasted the first time I
encountered this problem," because "I believed that two shapes with the
same-length perimeter should have the same area." After
several hands-on investigations, her "understanding
shifted." But she recommends: "don't take my word for it.
There's no substitute for firsthand experience, so try some
investigations for yourself."
Comment 1: If you know
about the perimeter and area of rectangles, you may quickly
find a counterexample to the "same
perimeter implies same area" conjecture.
For example, consider any rectangle with width = W and , length = 50 -
W. The perimeter is always 100, but the area can be as large as
625, if W = 25, and the area can be as close to 0 as desired, if W is
sufficiently close to either 0 or 50.
Comment 2: Marilyn Burns
recommends multiple
"investigations," so she doesn't appear to know that one
counterexample suffices to prove that the conjecture is
false.
Box Measuring Given a
20-by-20 centimeter piece of centimeter-squared paper, you can cut a
square from each corner and fold up to form an open-top
box. How many different size boxes can you make using this
method? Which of these boxes holds the most? The
problem is given on page 55. Marilyn Burns discusses it on page
page 257. She presents a 9 row table, giving the dimensions
and volume for the 9 whole number cases. The largest volume is
given as 588. This is found on the 3rd row [case that the side of
the cutout corner square is 3 cm]. The next largest volume is
given as 576. This is found on the 4th row [case that the side of
the cutout corner is 4 cm]. Marilyn Burns conjectures that
the largest volume is somewhere between these two cases. She
tries
3.5 cm and gets a volume of 591.5. Looks
promising! But she then ends the discussion by suggesting
"you may want to investigate what size square to cut from each corner
to
get the box of maximum volume." She quit!
Comment 1:
Quitting
was the only choice. Marilyn Burns isn't going to solve this
problem with her
"guess and check" approach. There are infinitely many
possibilities for "the different size boxes you can make," and kids
aren't going to easily discover "which of these boxes holds the
most." This isn't an appropriate problem for K-6 math or even
K-10 math, but it's a simple problem in differential
calculus. The volume V = H (20 - 2H)2. The
first
derivative V' = 400 - 160H + 12H2 = 4 (10 - 3H) (10 -
H). So
the maximum occurs when H = 3 1/3.
Comment 2:
Notice the prerequisite math knowledge and the time-consuming busywork
needed to produce Marilyn Burns' 9-row table. Also, notice that
if the "find the maximum volume" challenge was taken seriously, kids
could spend endless hours and never know for sure that they had found
the correct answer.
Lessons
from the Marilyn Burns
Website
If discovery-learning is taken to its
logical extreme, fewer teachers would be needed. Marilyn
Burns can't endorse that. And she's been around long enough
to know that math isn't discoverable. It's not natural.
It's an invented knowledge domain The no "teaching-by-telling"
fuzz is convenient for incompetent teachers, but awkward for someone
who is trying to make a living as a teacher of teachers.
So,
hoping that constructivist zealots won't notice the contradiction,
Marilyn
Burns promotes whole class
model lessons. Here
are four 5th
grade examples from her website.
- A
Fractions Lesson
- The first problem is to separate a 5 3/4 pound bag of candy
into 1/2
pound bags. How many 1/2 pound bags
will this yield? Three solutions are given. This is a very
easy mental math question. One student's solution correctly uses
formal
fraction division to find the answer of 11 of the small size bags,
leaving an extra 1/4 pound of candy. The other two
students use constructivist problem-solving
strategies. These methods involve drawing pictures showing 5
boxes divided into
two
half boxes and one more (slightly smaller) box divided into two parts,
one part labeled 1/2
and the other part labeled 1/4. The drawings are
accompanied by lengthy written
explanations.
- Comment:
These constructivist methods are inefficient, don't
generalize to more difficult problems, and give no indication that the
student knows how to set up and solve the appropriate problem in
fraction division.
- Later in this lesson a second problem requires
dividing 96 by 7 7/16. According to the teacher, "no one knew
what to do." So she "encouraged them to use constructivist problem-solving strategies.
She suggested that they make a model. First they cut
out a strip from used file folders that measured 7 7/16 inches long.
Then they measured and marked with masking tape 8 feet (or 96 inches)
on
the classroom floor. Then they "carefully measured out 12 pieces
of 7 7/16 inches each
from 96 inches" and concluded that 96
÷ 7 7/16 is "about
12."
- Comment:
Recall the "estimates are better than exact"
quote given above. This gives the impression that
Marilyn Burns math graduates would know how to quickly estimate the 96
÷ 7 7/16 fraction
division, but the students here don't appear to know that 8 x 12 = 96,
so they resort to hands-on methods to arrive at their estimate. This
isn't a simple problem in fraction division, but by the end of the 5th
grade the student should be able to show that the exact answer is (96
x 16)/119. If an approximation is desired, the student should
realize that an easy cancellation occurs if 119 is approximated by 12 x
10. This yields (8 x 16)/10 = 12.8 as a reasonable
approximation.
- Comparing
Fractions with Fifth Graders: Marilyn Burns first reports
that she knows about the standard way to compare fractions by
converting to a common denominator. But she wants kids to
develop their own personal ways to compare fractions. She writes:
"To help students learn to compare fractions, I used several types of
lessons. I gave students real-world problems to solve, such as sharing
cookies or comparing how much pizza different people ate, and had class
discussions about different ways to solve the problems. I gave them
experiences with manipulative materials—pattern blocks, color tiles,
Cuisenaire rods, and others— and we explored and discussed how to
represent fractional parts. I taught fraction games that required
them to compare fractions, and we shared strategies. At times I just
gave them fractions, and we discussed different ways to compare
them."
- Comment:
Marilyn Burns is wasting valuable time. Children need to master
the standard method for comparing fractions. It's a simple
skill, but important background knowledge, necessary for later mastery
of traditional algebra.
- A
Remainder of One After many examples of whole number
division (such as 9/4 and 13/6) yielding the answer 2 R1 (2 plus a
remainder of 1), the 5th grade students are asked if there is a
number N
such that 10 divided by N equals 2 R1. Alexis "came up with the
answer of N = 9/2." Prior to this point, all examples were
limited to a whole number divided by a whole number. But Alexis
has now given a rational number (fraction) solution.
- Comment:
Marilyn
Burns wants us to be impressed with the out of the box thinking, but
she's misleading the students and has missed an important teaching
point. The remainder concept is only necessary for the whole
number context. It's an accommodation that's needed because the
whole numbers aren't closed
under division [when you divide a whole number by a whole
number, the result may not be another whole number]. Once we
extend to the
rational numbers (fractions), we no longer need the awkward concept of
remainder. The rational numbers are closed under division. The
answer to 10 ÷ 9/2 is
correctly written as 20/9 or 2 2/9, but not 2
R1.
- Counting
Crocodiles The 5th grade problem is to compute 1
+ 2 + 3 +
4 + 5 + 6 +7 +8 + 9 + 10. Jimmy said 57. Andrew and
Erin both said 55. After Kailen and Spencer both argued in
favor of 55, Jimmy caved in and agreed. All 5 now agreed.
Case closed.
- Comment:
Marilyn Burns missed a beautiful opportunity
to teach about a famous classroom "discovery." The class just decided
that 55 was the sum of the first 10 natural numbers. What
about the sum of the first 100 natural numbers? After they
struggled with that, she could have then told them how Carl
Friedrich Gauss (1777 - 1855) solved this problem when he was their
age. His teacher was trying to keep the class busy. (Back then
they admitted it.) But Gauss quickly produced 5,050 as the
answer. He recognized that he could quickly compute twice the
desired sum:
1.
( 1 + 2
+ 3 + 4
+ 5 + + . . .
+ 100) = S
2. + (100 + 99
+ 98 + 97 + 96 +
+ . . . .. + 1) = S
3. 101
+ 101 +101 + 101 + 101 + + . . . . +
101 = 100 x 101 = 2S
Therefore S = (100 x 101)
÷ 2 = 50 x 101 = 5,050
How Can
Phil Mickelson Help?
- First, help your own
children. Acquire the complete set of materials (12 textbooks and
12 workbooks)
for Singapore Math Primary
Mathematics U.S. Edition. These
24 books will cost a
total of $192 + S&H. This is an excellent
investment for
the math education of Amanda,
Sophia, and Evan.
- Read Ten Myths About Math
Education and Why You Shouldn't Believe Them.
- Read The
Math Wars by David Ross.
- Seek the opinion of mathematicians employed by
ExxonMobil.
- Get a copy of About
Teaching Mathematics: A K–8 Resource, by Marilyn Burns. Don't
take Bill Quirk's word for it. See for yourself.
- To better understand
how the National Council of Teachers of Mathematics (NCTM) has promoted
the constructivist mindset, read Understanding
the Revised
NCTM Standards: Arithmetic is Still Missing
- Know that Marilyn Burns has a major new problem. The NCTM
recently released their Curriculum
Focal Points. Here they finally recognize the
importance of standard arithmetic.
- To better understand the constructivist mindset, read A Summary View of NCEE Math.
- For more examples of constructivist K-6 "problem-solving
activities," see How the
NCEE Limits Elementary School Math . Here you'll find samples
of "student-invented" computational methods.
- Visit the Mathematically
Correct and NYC HOLD
websites:
- Please consult NYC HOLD's National Advisors.
We will be happy to answer your questions.
- Spend some time comparing About
Teaching Mathematics: A K–8 Resource, by Marilyn Burns, to Elementary
Mathematics for Teachers, by Thomas
H. Parker and Scott J. Baldridge. Which book rings
true? Which book helps you with the math education of your
three children?
- Finally, please speak out in defense of genuine math education
for American children. We know you and your wife Amy had the best
of intentions and must be shocked to discover that ExxonMobil has
appeared to endorse fuzzy math. An army of parents has also
been shocked by fuzzy math programs. These parents and their children
desperately need a champion to step up to
the tee .
Bill
Quirk is a graduate
of Dartmouth College and holds a Ph.D. in Mathematics from the New
Mexico State University.
Copyright 2007-2011 William G. Quirk, Ph.D.