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Fractions in Disguise: A Math Adventure

3.84  ·  Rating details ·  123 ratings  ·  37 reviews
When a valuable fraction goes missing, George Cornelius Factor (a.k.a. GCF) vows to track it down. Knowing that the villainous Dr. Brok likes to disguise his ill-begotten fractions, GCF invents a Reducera tool that strips away the disguise, reducing the fraction and revealing its true form. Equal parts of action and humor add up to a wholly entertaining introduction to ...more
Hardcover, 32 pages
Published March 25th 2014 by Charlesbridge (first published January 1st 2014)
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Average rating 3.84  · 
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Emily Foster
Oct 08, 2019 rated it liked it
The premise of this book is really nice, I really like how fractions are incorporated throughout and particularly how it includes mathematical definitions, language and some misconceptions (5/9 looks like a half but is just more). However, I found the book too wordy and quite hard to follow and could be so much easier if the really helpful and engaging illustrations were partnered with fewer words.
Jul 29, 2014 rated it really liked it
The author asked if I would review his newest math adventure book. I accepted as I enjoy his authorship of "Paradox in Oz". I am not a big math fan, but I was pleasantly surprised by this book and its fun and amusing puns. I also loved the illustrations by David Clark. It would be great for a reluctant reader who likes math or to use in a classroom to help kids understand how to simplify fractions. There is a longer description of fraction reduction in the back of the book.

The book is about a
Jan 03, 2015 rated it really liked it
George Cornelius Factor is a collector of fractions. George, who is 1/4 genius, 1/ stubborn, 1/3 determined and 1/6 crazy, goes to auctions in search of new fractions for his collection. And when someone steals the 5/9 that is being auctioned, George builds a "reducer" (1/2 ray gun and 1/2 calculator) in order to find the fraction that has been disguised.

A fun way to introduce students to reducing fractions. I'm anxious to show this one to my teachers to see what they think.
Mar 03, 2014 rated it liked it
Shelves: math, humor
Math teachers may want to add this book to their collection since it teaches about fractions in an entertaining way. George Cornelius Factor loves fractions; in fact, he even collects them. But when one that he has his eye on disappears, he confronts the mysterious Dr. Brok about its location. There is plenty of humor and lots of action and colorful illustrations even while students are learning about how to reduce fractions.
Cindy Minnich
Jul 03, 2014 rated it really liked it
I'm not sure what made me pick this book up, but I know that I was delighted when I saw my son's eyes light up - a sign that he'd figured something new out about the world. This book has a silly pun-filed whodunnit, an invention, and a great way to explain how and why to reduce fractions. I'm not sure what my elementary math teacher friends would say about it, but seeing this concept make sense to my son seemed good enough for me.
May 14, 2014 rated it really liked it
In fact there are even people who collect fractions. I know it's hard to believe it's true but in Fractions in Disguise: A Mathematical Adventure (Charlesbridge) written by Edward Einhorn with illustrations by David Clark, three people are victims of an evil mind.

Full review:
Kate Hastings
Jul 07, 2014 rated it really liked it
Shelves: math-and-science
Grades 3-5. Reducing fractions has never been so fun! A fraction has been stolen from a math auction and the thief has disguised it by creating an equivalent fraction. George Cornelius Factor invents the "Reducer" to help identify the stolen fraction and save the day. It would be fun to have students create their own "reducer rays" and act out the story with other fractions.
Jan 30, 2015 rated it really liked it
Cute story about reducing/simplifying fractions. Love the illustrations and creative names! This book might be good for a 3rd-4th grade read aloud. I would give this book 5 stars, but the transition between the pages didn't go as smoothly as I would have liked. However,it is still a good book for the subject and I still recommend it!
The Brothers
Jan 16, 2016 rated it really liked it
Asher (8yo) got a LOT more out of this book than Dexter (5yo), though Dexter seemed to enjoy it nonetheless and sat through it without complaint. A collector of fractions hunts down a stolen one by using a device he constructed called the Reducer.

The illustrations really are superb.
This is a great book for students who are learning about fractions! There are fractions on every page, jokes to go with them, and a mystery to solve. In order to solve the mystery, though, one must know about fractions. It's a fabulous and fun read for elementary school students!
Jen Yonit
Nov 26, 2015 rated it it was amazing
Shelves: children-s
My 8 and 9 year olds loved this book. They have read and reread it. Definitely going to look out for more books by this author!
Maggi Rohde
I've read several of the Charlesbridge Math Adventures before. This is a fun mystery that teaches concepts about fractions, specifically reducing them.
Maria Caplin
Fun story could be interactive with students using dry erase boards. Fun addition to math workshop mentor text.
Brenda Kahn
This zany story felt a bit like those "Perils of Pauline" silent movies that feature madcap antics complete with a mustachioed villain. Nice addition to upper elementary math classrooms.
Mar 20, 2017 rated it really liked it
Shelves: read-to-the-kids
This was a cute idea. It did a decent job of making what could be a dry subject into something more fun. If you are a math nerd, you can get your nerd on.
May 06, 2015 rated it it was amazing
A wonderful book about simplifying fractions and leads into discussions about adding fractions. A book for any middle level to upper elementary math teacher. Excellent classroom resource.
Feb 16, 2015 rated it really liked it
Clever story about reducing fractions.
Feb 01, 2017 rated it really liked it
This is the best way to learn #fractions!
Feb 04, 2015 rated it it was amazing
Shelves: i-d-recommend
I thought this was positively charming! I loved the puns, the pictures, and the characters. This really made me smile. Over all a fun read.
Bridget Elliott
Feb 28, 2016 rated it really liked it
Shelves: math-books
Cute book to use as part of your fractions (equivalent fractions or reducing fractions) unit!
May 27, 2014 rated it liked it
This was a book that incorporated upper elementary math, and there certainly aren't many of them. The illustrator is from Va.!
Tracy Holland
Jun 20, 2016 rated it really liked it
This is a great book for teaching equivalent and reducing fractions, with a cute story to go with it.
Dec 27, 2019 rated it it was ok
Shelves: math
The book presents the mechanics of finding fractions that are equivalent to each other pretty clearly (though not with any cleverness about the numbers), but it's really not drawing on images or thinking about the slices that make up fractions here at all.

The story also feels like it cheats to me; the 34/63 is a bit obscured when we see it, so it doesn't appear that there's a missing piece. (You can see the center of the circle, and it *definitely* looks like nothing is missing.) The 1/63 slice
Jaden Craig
Apr 02, 2020 rated it it was amazing
Shelves: mystery
Factions in Disguise: A Math Adventure by Edward Einhorn is a fun book about a very coveted fraction that vanishes out of thin air. After this mysterious disappearance, George Cornelius Factor then begins doing everything in his power in order to find the missing fraction. I would use this book in my future classroom to introduce simplified and reduced fractions with equal parts in a fun and humorous way.
Jo Oehrlein
Dec 29, 2019 rated it it was ok
Shelves: math, picture-books
Feels like this gives no intuition at all about different names for the same fractions.

And really, if a slice was missing from the 34/63, then it was either 34/62 (in which case it would reduce), or there should have been a openly blank piece (none of the fractions shown ever have a gap in the circle -- they're all represented as whole pies with parts shaded).
Jul 17, 2018 rated it it was amazing
Shelves: to-buy
What a truly fun math adventure!!! Fractions are enjoyable and interesting in this tale. Although I didnt love the illustrations, they did take away from the wonderment of the book! Classroom must have for fraction lovers!! ...more
Mar 18, 2019 rated it liked it
I thought it was adorable and clever and fun but my nine year old was pretty darn meh about it.
David Molnar
Aug 01, 2014 rated it it was ok
Shelves: juv-math
meh. I didn't find anything inspiring here. Fractions have equivalent forms, evidently. I wouldn't even mind that being the entire plot if there were some kind of explanation as to why, for example, 10/15 is equivalent to 2/3. One thing that you can do in a picture book is to use the pictures to explain things. Instead, reducing a fraction is presented very mechanically. A missed opportunity.

(from my not-really-a-blog at
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Edward Einhorn is a writer/theater director, based in New York. He has written plays about neurology; picture books about math; adaptations of sci-fi novels; translations of French and Czech absurdists and of ancient Greek drama; puppet theater; modern Oz novels; explorations of economic theory; autobiographical found text dramas; midrashim on Jewish cultural icons; a libretto for an oratorio; and ...more

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