the writing on the wall- do the math.pdf

7/31/2019 The writing on the Wall- Do the Math.pdf

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Math Do the

The Writing

on the

Wall by Wendy Lichtman


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To the memory of Theresa Podmele, the first woman I knew who had a Ph.D. inmathematics. She taught my high school algebra class with passion and clarity, and

nearly fifty years later I still love the subject.


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Chapter 1 Patterns 1

Chapter 2 Three Thirds 15

Chapter 3 The Four Fours 28

Chapter 4 Graphs 35

Chapter 5 Formulas 48

Chapter 6 Codes 61

Chapter 7 Collecting Data 69

Chapter 8 Knives and Fires 80

Chapter 9 Absolute Value 93

Chapter 10 Rate of Change 104


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Chapter 11 Graphic Stories 113

Chapter 12 The Real Story 127

Chapter 13 Coincidental Systems 135

Chapter 14 No Formulas 150

Chapter 15 Family Patterns 164

Chapter 16 Tessellations 179

Chapter 17 Simplifying Expressions 188

Chapter 18

(Which, in Algebra,

Means Change) 201

Chapter 19 Probability: What Are

The Chances? 210

Acknowledgments

About the Author

Credits

Cover Copyright

About the Publisher


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Chapter 1 Patterns T here was this tagger in Los Angeles, Sammy

said, who wrote coded messages about who was

going to get murdered next. He knew that only one

person in the city could figure out what he wrote,

and that person did figure it out, but not until about

six people were already dead. Sammy turned away

from the graffiti wall to face Miranda and me. From

then on, she said, the murders stopped.

Even though Sammy does know a million facts,

shes so dramatic that its always hard to know if what

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shes telling you is accurate or a major exaggeration .

Thats creepy, Miranda said.

We only had about five minutes before school

started, and I wasnt really all that interested in

checking out the graffiti Sammy was so excited

about. But when she said, What Im thinking is that

this could be a warning, too, and that the person who

wrote it knew Tess would understand it, I looked at

the numbers that were painted on the back wall of

the church near our school.

There were about twenty bright green fours in the

bottom corner, styled in a way that made it look like

art all different sizes and shapes but still fours.

They formed a messy circle, so I had to tilt my head

from side to side to figure it out.

Do you understand it? Miranda asked as she

handed me her denim jacket and took my white sweat-

shirt. Miranda used to be smaller than Sammy and me,

but ever since we got to eighth grade shes the tallest one shes about two inches taller than me now, and

Im about two inches taller than Sammy. It doesnt

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really matter, though we still always share our clothes.

I think its the Four Fours problem, I said, slipping

on Mirandas jacket. Its one of Ms. Saltzmans favorite

things she gives us these for warm-up at math team

practice. Youre supposed to be ab le to make nearly any

number by using exactly four fours, I explained.

Like this oneI pointed to 4x4- _ would be

the number fifteen.

Clever, Miranda said.

I knew youd know, Sammy said. What Im

thinking is that maybe this is like that guy in LA,

and someone is telling you the next thing that

Richards going to do to you.

Oh, come on, I said, picking my backpack up

from the ground and tossing it over one shoulder.

Richard probably doesnt even know the next thing

hes going to do to me.

Samm y shrugged. Im not saying for sure; Im just

saying maybe. Stop scaring her, Miranda said as the three of us

headed toward school.

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I had known that Richard would do something to

get back at me for turning him in, but I thought it

would be something big maybe something so

awful that Id want to transfer out of Westlake.

Instead, though, he was making me suffer by doing

a lot of little mean things in the three weeks since

we got back to school from winter break.

In a way, I thought as I opened my locker and saw

the folded piece of paper that had been slipped

through the slats on the locker door, that can be

worse because then youre always waiting for the

next bad thing to happen. Also, you have to spend

your time wondering if hell e ver be finished.

I unfolded the note about five times before I got

to the words that said, Watch out, snitch. Miranda

was standing next to me, and even though I was

trying not to be scared, I could tell that she was or

maybe she just looked that way beca use she wasnt

used to wearing glasses. She had gotten a pair over the break, and after reading the note she looked at

me over the top of her glasses, not through the

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