# My dad's Easter rant

Discussion in 'Debate & Marathon Threads Archive' started by DrivingPigeon, Apr 6, 2015.

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1. ### DrivingPigeonPhenom

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Apr 6, 2015

Yesterday my family was at my grandma and grandpa's house for Easter when my dad decided to give us a math problem to solve. He said that he saw it on facebook with a note that said "50% of people will get this wrong." He said that he's shown it to "hundreds" of people, and young people get it wrong because of the "new math" that we're learning these days. He said that he gave it to a high school math teacher, who looked at it for a long time, and got it wrong.

Before showing it to us he said that my grandma and aunt would get it right, but my husband and I would probably get it wrong, because we were taught this "new math." I thought that was pretty entertaining, because my husband and I were the only 2 in the room with a college education, and my husband is an electrical engineer. He graduated 3rd in his class from a top engineering school, and has taken the highest level math classes offered.

This is the problem that he gave us: 7 + 7 / 2 x 8 - 6

What do you get for an answer? What do you think my dad thinks the answer is (hint: he's wrong )?

3. ### comabaCohort

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Apr 6, 2015

29

Did he get 50?

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Apr 6, 2015

29

5. ### DrivingPigeonPhenom

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Apr 6, 2015

Yes!

My husband and I both got 29, and my dad kept telling us that we were wrong, because of the "new math" that we were taught. We tried to explain order of operations, but he kept telling us we were wrong and that the problem was so simple. I'm embarrassed for him, because he's obviously showing this to a lot of people (he bartends on the weekends), and he doesn't even know the right answer.

The best part was his rant about how kids these days are taught math in such weird ways. He also went off on a rant about how kids aren't taught history anymore in schools. It was so difficult for me not to say anything, but I really didn't want to get into it.

6. ### czaczaMultitudinous

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Apr 6, 2015

Omg. Sounds like my MIL. FIL is a retired hs math teacher and administrator. He now is an adjunct and teaches math remediation at a small college. My MIL pontificates on common core ALL THE TIME and how her girlfriend retired because the standards drove her out and how good teachers are leaving(more like she was eligible for retirement and pension funding threats being what it is, she went...) MIL wouldn't be able to do that math problem. FIL would.

7. ### MikeTeachesMathDevotee

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Apr 6, 2015

It's especially difficult being a math teacher under common core. You have to deal with all kinds of stupid opinions.

8. ### brosPhenom

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Apr 6, 2015

The answer is 29 because the way it is written, there are no parentheses to define how it should be done.

So it becomes:
7+((7/2)*8)-6

9. ### czaczaMultitudinous

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Bros,why did you feel you needed to google for the answer? Aspects of order of operations are taught as early as grade 3.

10. ### swansong1Virtuoso

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Apr 6, 2015

Common core has not changed order of operations, to the best of my knowledge. I would have figured it out the same before and after CC.

11. ### czaczaMultitudinous

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Apr 6, 2015

:thumb: good old PEMDAS!

12. ### DrivingPigeonPhenom

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Apr 6, 2015

Exactly. I'm so tempted to send my dad the Khan Academy video on order of operations, along with an explanation of its origin. I'll think I'll just let it go, though. :thumb:

13. ### lucybelleConnoisseur

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Apr 6, 2015

I always see these "math" challenges on facebook. I think they're silly. If anyone really wanted someone to solve that they would put parenthesis on the freaking thing!

*LB's rant over*

I also got 29 easily. For a second I thought you all were saying that was the wrong answer and I was like whhaaa?

14. ### stephenpeConnoisseur

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Apr 6, 2015

When I read it like this
7+7
2x8-6

I get 14 divided by 10 or 1 2/5

15. ### czaczaMultitudinous

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Apr 6, 2015

You aren't applying order of operations.

7 + 7 / 2 x 8 - 6

You'd do 7/2 first=3 1/2

Then multiply by 8. 8x3 1/2 = 28

Then 7+28= 35

Subtract 6. 35-6=29.

16. ### TeacherGroupieModerator

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Apr 6, 2015

Um, it's not quite that simple.

Had the expression been written with the obelus or standard division sign, ÷, like this,

7 + 7 ÷ 2 × 8 – 6 ,​

then, yes, the order of operations goes forth as czacza indicates and the result is 29.

But the symbol that's in play isn't ÷, it's /. Whether that symbol is called "slash", "diagonal", "solidus", or "virgule", it's not ONLY a division sign: instead, it is used in an inline fraction (that is, a fraction that is typeset as one line) to separate the numerator from the denominator.

As Wolfram Mathworld notes with a less spectacular example, is that the resulting expression IS still ambiguous: we don't know just how much of what's before / is intended to be numerator nor how much of what's after / is intended to be denominator. That is, our 7 + 7 / 2 × 8 – 6 contains a fraction, and, according to math's rules of punctuation, that fraction really and truly COULD be any of the following:

7
8

7 + 7
_ 2

___7___
2 × 8 – 6

7 + 7
2 × 8

___7___
2 × 8 – 6

__7 + 7_
2 × 8 – 6

Using any of these vertical fractions disambiguates matters in a hurry, but they are more than slightly a pain to produce. To see how I did these, choose Reply-With-Quote. The fractions will look extremely untidy. The typographical untidiness goes far toward explaining why the solidus even exists distinct from the obelus.

On behalf of my mathematician friends, let me beg everyone please when writing math to provide such parentheses as are necessary to make things clear, and to avoid using / or solidus unless you actually do intend a fraction. (Typing an obelus on a Mac is pretty easy: it's Option-/. I expect that it isn't much harder on a PC.)

17. ### DrivingPigeonPhenom

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Apr 6, 2015

Uhhh...I didn't know how to do the division symbol. I thought about explaining that the / was in place of the division symbol, but I assumed people would just figure it out. And they did.

But thanks for all of that.

18. ### czaczaMultitudinous

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Apr 6, 2015

:lol:

I've never thought about a keyboard not having the 'division sign', but good we understood what you meant.

19. ### TeacherGroupieModerator

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Apr 6, 2015

It can be disconcerting when a story turns out to be less cut and dried than one thought, yes.

Turns out, by the way, that the notation that we all grew up with for long division is really rather recent - enough so that the sign for it (which looks like it was cobbled together from a left parenthesis attached to a horizontal line, because it WAS cobbled together from a left parenthesis attached to a horizontal line) doesn't have its own name. See http://jeff560.tripod.com/operation.html.

20. ### vickilynMagnifico

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Apr 6, 2015

Wow, I thought I was the only person not seeing it as clear cut, and now I can understand why. I truly thank you.

21. ### brosPhenom

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Apr 7, 2015

Order of Operations might be taught that early now. I was taught it in eighth grade (Pre-Algebra, or at least that was what was taught at the time).

Because I couldn't figure that out mentally. Last time I had to do any kind of rigorous mental math was my neuropsych eval in 2010, before that, sometime in high school when we weren't allowed to use calculators.

If I were to try to solve it without a calculator, I would proceed as follows:
7+7/2*8-6
PEMDAS (Parentheses, Exponent, Multiplication, Division, Addition, Subtraction)

No P or E. so lets do M, as that is what comes first.

2*8

16
7+7/16-6

There's D

7/16 = 7/16

7+7/16-6

There's A
7+7/16 = 7 7/16

7 7/16-6

Now there's S

7 7/16-6

1 7/16

Yeeeeah

I have no idea how or why you can change the order of operations like that. It is PEMDAS, not PEDMAS.

alt+0247 (on the numpad) ÷ for windows users.