# Math quiz

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#### rklapp

##### NAR# 109557
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If referring to the pixelated version of the shape, then 2. If the symbolic version, then none because it will never be a right angle at the infinitesimal scale.

Now...

PEMDAS vs BODMAS

#### Cape Byron

##### The BAR formerly known as Skippy-2
TRF Supporter
Mum...! Nice people are hurting my brain!

Ummm... 9?

#### Sooner Boomer

##### Well-Known Member

Why? PEDMAS

Step 1: Parentheses

Step 2: Exponents

Step 3: Multiply

Step 4: Divide

Step 6: Subtract

So the order would be:
(1+2)=3
2x3=6
6 / 6 =1

#### dhbarr

##### Amateur Professional
THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER

#### jsdemar

##### Well-Known Member
If referring to the pixelated version of the shape, then 2. If the symbolic version, then none because it will never be a right angle at the infinitesimal scale.

Now...

View attachment 452433
PEMDAS vs BODMAS
9.

#### Funkworks

##### Well-Known Member
I was taught not to use the ÷ sign because of that kind of confusion. When you write the following instead, there is no ambiguity:
$x=\frac{6}{2(1+2)}$
or
$y=(\frac{6}{2})(1+2)$
I've never seen the ÷ sign in a scientific or engineering textbook or professional paper.

As for the half circle question, I would agree, but I suspect a mathematician having gone through non-Euclidean geometry would also have interesting answer. There might be a way to express an answer using limits but I haven't quite nailed it.

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#### wonderboy

##### Active Member
Step 1: Parentheses

Step 2: Exponents

Step 3: Multiply

Step 4: Divide

Step 6: Subtract
I was taught that multiplication and division (Step 3 & 4) were of equal "priority" so when faced with both, work left to right. Same with addition and subtraction (Step 5 & 6).

So given that, I break down first step as: 6 / 2 * 3, and then work left to right: 3 * 3 = 9 .

I also agree that I hate equations written in somewhat ambiguous form. When in doubt, I usually over constrain with parentheses.

#### David Schwantz

##### Well-Known Member
TRF Supporter
Because I can see them

#### jsdemar

##### Well-Known Member
As for the half circle question, I would agree, but I suspect a mathematician having gone through non-Euclidean geometry would also have interesting answer. There might be a way to express an answer using limits but I haven't quite nailed it.
I would begin the proof with some definitions: a tangent line intersects a curve at a single point; a line must have at least two points; a right angle is the intersection of two lines with angle exactly 1/4 a revolution; the bisector of a circle intersects only two points on a circle. Working from there, the figure cannot have any right angles because the "corner" is a single point. The tangent line at the intersection will have a right angle, but it only shares a single point with the shape in the figure.

##### Well-Known Member
TRF Supporter
Just bisect the half circle and you have two right angles.

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#### BABAR

##### Builds Rockets for NASA
TRF Supporter
If referring to the pixelated version of the shape, then 2. If the symbolic version, then none because it will never be a right angle at the infinitesimal scale.

Now...

View attachment 452433
PEMDAS vs BODMAS
Poorly written equation for precisely the reason that causes the confusion.

To me, a good writer would “phrase” the equation in a manner that would not allow any doubt. Unfortunately, people are inherently lazy. Meconium happens, but it is particularly frustrating when easily AVOIDABLE meconium happens.

sort of like many Model Rocket instructions.

I remember my Japanese instructor in college, Fujita-Sensei, saying, “KISS, Cadet-san, KISS.”

translated, “Keep It Simple, Stupid.” Some things transcend language differences.

#### BABAR

##### Builds Rockets for NASA
TRF Supporter
In sixth grade they bused some of us up to the high school to take a physics class.
Our teacher talked about how someone had estimated the cicumeference of the earth using rods and shadows and known distances and angles. I think it was Eratosthenes method,

we were given cheap plastic globes and sticks and protractors.

I didn’t have a clue how to do it, but the globe unscrewed, and I measured the diameter and multiplied by Pi. I didn’t show my work because I knew that wasn’t how it was supposed to be done.

Mr. Engel has long since passed to where he can likely see and measure the Earth and all the celestial bodies easily and directly at his leisure. But there are around 18 people around 6 years older than I am who still don’t know (nor I am sure who care or even remember) how the sixth grader was the only one who got the right answer.

#### neil_w

##### Good at some things
TRF Supporter
The semicircle question was posted to Twitter by a Dad who was working with a 7 year old on their math homework. It is an appallingly badly constructed question.

false.

Full story:

#### SkyFire

##### Well-Known Member
Simple equation? Let's see if you can get it right;
50 + 50 - 25 x 0 + 2 + 4 =

##### Well-Known Member
TRF Supporter
Simple equation? Let's see if you can get it right;
50 + 50 - 25 x 0 + 2 + 4 =
6

Nope!

TRF Supporter
106

#### Funkworks

##### Well-Known Member
Simple equation? Let's see if you can get it right;
50 + 50 - 25 x 0 + 2 + 4 =
Don't mind me, practicing Latex:

x = 50 + 50 - 25 x 0 + 2 + 4
x = 50 + 50 - (25 x 0) + 2 + 4
x = 50 + 50 - 0 + 2 + 4
x = 50 + 50 + 2 + 4
x = 106

Um ... darn. Didn't get to use Latex.

#### SkyFire

##### Well-Known Member
Ding, ding, ding, we have a winner!
Reason; The order of operation in an equation is to do multiplication first.

#### PhlAsh

##### Well-Known Member
You say PEDMAS but you perform PEMDAS. Division takes priority over Multiplication because Division is Multiplication to the -1 Exponent.

Hmmm... My quote of SoonerBoomer got thrown out...

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#### Funkworks

##### Well-Known Member
Not especially but your thread about Latex coincides with people at work talking about it and me realizing that learning it again could be useful (for work).

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#### Funkworks

##### Well-Known Member
I learned Latex while using another forum long ago and forgot about it. I just found out how to use it here, so if I get quick enough, it might supercede my alternatives.

#### Thundercloud

##### Well-Known Member
I typed it into Excel like it was typed in the question, and got 9.

#### Mike Haberer

##### Well-Known Member
TRF Supporter
THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER
Agreed. By stating an answer of 2 the assumption is being made that the curved portion of the figure is intersecting the line at a right angle, but that could be a false assumption. The curved portion of the figure could be intersecting at an angle of 89.99 degrees with the line, which would look like but not be a right angle and the answer would be zero. Precision, in description and measurement, matters.