# This is how they're teaching fractions? **URL:** \ **Category:** The BBQ Pit\ **Created:** [November 11, 2010, 2:12am UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264 "2010-11-11T02:12:25Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [November 11, 2010, 3:20pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/21 "2010-11-11T15:20:31Z")
> [@Boyo\_Jim](#): > > I blame society. Well, that settles it then. šŸ˜ƒ ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [November 11, 2010, 3:37pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/22 "2010-11-11T15:37:20Z")
> [@Boyo\_Jim](#): > > I blame society. Noā€¦ itā€™s George Bushā€™s fault! ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [November 11, 2010, 3:47pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/23 "2010-11-11T15:47:17Z")
> [@Crafter\_Man](#): > > Noā€¦ itā€™s George Bushā€™s fault! Well, of course. But which one of them? ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [November 11, 2010, 5:51pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/24 "2010-11-11T17:51:03Z")
> [@Boyo\_Jim](#): > > Well, of course. But which one of them? Yes ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [November 11, 2010, 5:58pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/25 "2010-11-11T17:58:24Z")
> [@fjs1fs](#): > > Whatā€™s even funnier is that even if you needed to find lowest common denominator, it would have been 4, not 8! For the algorithm to work, you only need a common multiple, not the least common multiple. Itā€™s easier to teach them to get a common multiple of a and b by multiplying together. You do need to reduce to the lowest terms in the final answer, but you have to do that if youā€™re working with the LCM anyway. ---
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [November 11, 2010, 6:09pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/26 "2010-11-11T18:09:21Z")
That is a half-assed way of teaching fractions. ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [November 11, 2010, 6:14pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/27 "2010-11-11T18:14:32Z")
> [@The\_Second\_Stone](#): > > That is a half-assed way of teaching fractions. What I just posted? Yes, it is half-assed: it makes the algorithm a bit easier, but at the expense of the student not understanding whatā€™s going on. It would make more sense as a computer algorithm, since a computer doesnā€™t understand anything. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [November 11, 2010, 6:44pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/28 "2010-11-11T18:44:56Z")
I think, though Iā€™m not sure, that **The Second Stone** is referring to the OP, not your post, **Giles**. I think itā€™s actually great to point out to students that you donā€™t need the least common multiple, just any common multiple, and that one easy way to get a common multiple is by taking the product. Come to think of it, I donā€™t remember how we were taught to get least common multiples, or even if we were taught a way to do so beyond ā€œJust know itā€. I think itā€™s even worthwhile to also point out that thereā€™s no _need_ to reduce fractions to lowest terms, except as one may self-impose a desire to do so. (Not quite the same topic, but coming to mind nonetheless in discussing reducing to lowest terms, it annoys me to no end when (college) students of mine run screaming away from having square roots in denominators; ā€œBut we have to move them to the numerator!ā€ ā€œNo, you donā€™t.ā€ ā€œButā€¦ butā€¦ā€ ā€œYouā€™ve been trained to always put things into a certain standardized form, but thereā€™s nothing to be gained by this except when you have some need for that standardizationā€. Showing that itā€™s perfectly fine to treat multiple representations of the same number on equal footing early and often would perhaps help avoid this kind of thinking.). ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 11, 2010, 7:32pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/29 "2010-11-11T19:32:27Z")
> [@Giles](#): > > What I just posted? Yes, it is half-assed: it makes the algorithm a bit easier, but at the expense of the student not understanding whatā€™s going on. It would make more sense as a computer algorithm, since a computer doesnā€™t understand anything. You donā€™t need common multiples in the denominator to multiply fractions, it achieves nothing, makes extra work, and obscures whatā€™s going on. It would not make one-third of four-fifths of three-quarters of fuck-all sense as a computer algorithm either. Multiply the numerators, divide by the denominators - if you like, multiply the denominators and divide into the product of the numerators; better yet, simplify down if either of the numerators have common factors with either of the denominators. Good luck working out 1/2 x 2/3 x 3/4 x 4/5 x 5/6 x 6/7 x 7/8 x 8/9 by the common denominator method. But by the direct method, itā€™s piss easy. All the numerators and all the denominators cancel except 1 and 9 respectively, leaving 1/9 as the answer. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [November 11, 2010, 7:35pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/30 "2010-11-11T19:35:02Z")
Iā€™m sure **Giles** was referring to the comment regarding the hypothetical situation where addition were being carried out instead; **Giles** was noting that, were it addition, there would be nothing wrong with using a common multiple other than the least common multiple, and that using the product is particularly convenient. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 11, 2010, 7:50pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/31 "2010-11-11T19:50:19Z")
Heā€™s quite right as to that, of course. ---
**Author:** ![Gestalt](https://avatars.discourse-cdn.com/v4/letter/g/90ced4/32.png) [@Gestalt](https://boards.straightdope.com/u/Gestalt)\ **Post date:** [November 11, 2010, 7:57pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/32 "2010-11-11T19:57:09Z")
> [@Crafter\_Man](#): > > I teach math to liberal arts students at the college level. Let me just say that the math skills of my students are truly deplorable. Upon entering my class, most cannot add or multiply fractions, let alone solve an equation like 4b = 12. > > Something is \*very \*seriously wrong with how mathematics is being taught at the elementary and HS levels. Yeah, a lot of people seem pretty retarded at very basic math . . . like even ā€œgrocery-storeā€ math, figuring out what some % off will be or estimating totals or how to calculate tips. In fact, most of the people I know who have a good intuitive grasp of numbers are engineers or hard (non-biological) science-types. Move even into biological sciences and people are lost. Letā€™s not get started on the English majors. ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [November 11, 2010, 8:01pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/33 "2010-11-11T20:01:51Z")
> [@Indistinguishable](#): > > Iā€™m sure **Giles** was referring to the comment regarding the hypothetical situation where addition were being carried out instead; **Giles** was noting that, were it addition, there would be nothing wrong with using a common multiple other than the least common multiple, and that using the product is particularly convenient. Yes: for multiplication thereā€™s really no reason to find the LCM for all the fractions. > [@Gestalt](#): > > Letā€™s not get started on the English majors. Objection: my first degree was an English major, but I did round off my education by completing the equivalent of a mathematics major four years later. ---
**Author:** ![kiz](https://avatars.discourse-cdn.com/v4/letter/k/7feea3/32.png) [@kiz](https://boards.straightdope.com/u/kiz)\ **Post date:** [November 11, 2010, 9:10pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/34 "2010-11-11T21:10:38Z")
> [@AWB](#): > > One big problem I see is that lessons today have to be all touchy-feely, everybody-have-fun, nobody-gets-left-behind sorts of affairs. Going to stations around the room, having worksheet/puzzles that tell corny puns, give-them-multiple-choice-so-theyā€™ll-have-a-25%-chance-of-getting-it-right. We had to memorize multiplication tables, unit circle chart (trig), and rules of fractions. Now, those things have to be posted on the walls somewhere for the students to refer to at any time. If math had been taught that way when I was in grade school, I probably would have aced it. I too had the ā€œmemorize the multiplication tableā€ and other methods mentioned. It was painful. I couldnā€™t make heads or tails of anything. Fractions? Percentages? :eek::eek::eek: Hell, I still canā€™t make heads or tails out of fractions unless theyā€™re the common 1/4, 2/3, and such. Throw me a problem similar to what your students had on that test and Iā€™d still be sitting there šŸ˜• ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [November 11, 2010, 9:36pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/35 "2010-11-11T21:36:51Z")
> [@Gestalt](#): > > In fact, most of the people I know who have a good intuitive grasp of numbers are engineers or hard (non-biological) science-types. Move even into biological sciences and people are lost. Letā€™s not get started on the English majors. I_M_E, the people I know who have the biggest problems with simple math are the ones who are the best at the hardest stuff (the ones who are, e.g., PhD engineering students). I should probably also point out that my BA is in English, my minor was CompSci, and I had AP Calc in high school before getting sick of math. ---
**Author:** ![RTFirefly](https://avatars.discourse-cdn.com/v4/letter/r/c77e96/32.png) [@RTFirefly](https://boards.straightdope.com/u/RTFirefly)\ **Post date:** [November 11, 2010, 9:53pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/36 "2010-11-11T21:53:44Z")
> [@Boyo\_Jim](#): > > I blame society. I think we should blame the images on TV. ---
**Author:** ![asterion](https://avatars.discourse-cdn.com/v4/letter/a/4da419/32.png) [@asterion](https://boards.straightdope.com/u/asterion)\ **Post date:** [November 11, 2010, 10:10pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/37 "2010-11-11T22:10:57Z")
> [@RTFirefly](#): > > I think we should blame the images on TV. I blame Canada. ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [November 11, 2010, 10:14pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/38 "2010-11-11T22:14:16Z")
I blame the snake in the Garden of Eden ā€“ it was an adder, so it couldnā€™t multiply fractions. ---
**Author:** ![Bosstone](https://avatars.discourse-cdn.com/v4/letter/b/22d042/32.png) [@Bosstone](https://boards.straightdope.com/u/Bosstone)\ **Post date:** [November 11, 2010, 10:24pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/39 "2010-11-11T22:24:50Z")
I canā€™t stand all this division! ā˜¹ ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [November 11, 2010, 10:37pm UTC](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264/40 "2010-11-11T22:37:19Z")
> [@Indistinguishable](#): > > (Not quite the same topic, but coming to mind nonetheless in discussing reducing to lowest terms, it annoys me to no end when (college) students of mine run screaming away from having square roots in denominators; ā€œBut we have to move them to the numerator!ā€ ā€œNo, you donā€™t.ā€ ā€œButā€¦ butā€¦ā€ ā€œYouā€™ve been trained to always put things into a certain standardized form, but thereā€™s nothing to be gained by this except when you have some need for that standardizationā€. Showing that itā€™s perfectly fine to treat multiple representations of the same number on equal footing early and often would perhaps help avoid this kind of thinking.). Why _do_ they insist on deradicalizing the denominator, anyway? I had an algebra teacher once with a big stick up her ass about that, and I never saw the point. x = 3/sqrt(5) is just as good an answer as x = 3( sqrt(5)/5 ). Easier to type, too. [Previous page](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264.md?page=1) [Next page](https://boards.straightdope.com/t/this-is-how-theyre-teaching-fractions/560264.md?page=3)