Posted on 04/12/2011 1:32:09 PM PDT by grundle
Texas Instruments TI-85 says:
48÷2(9+3) = 2
But Texas Instruments TI-86 says:
48÷2(9+3) = 288
Yup, you know it, my friend!
Quod Erat Demonstrandum!
:)
Cheers
Truth!
Unfortunately, with the way single-line expressions are parsed, you do indeed need those parentheses if you want the answer to be 2.
Yeah, I know, and it's killing me, because I was actually taught to assume those extra parenthesis (see post 600). Visual aides were the only thing to get me through math. I mean, I still use:
is over of = % over 100
to figure out tips and things like that.
I suck at math.
Just move the decimal point over one for 10%. Double that to tip 20%, estimate between the two for rates inbetween. ;-)
(blinks)
(looks at it again)
Seriously?! Well crap. You know I sat there and figured for 20%.
I knew to move it over for 10%, that was easy. It absolutely never occurred to me to just double the 10% value to get 20%.
(sigh) LOL.
Thanks SD, that is the best practical advice I have ever received on tip figuring.
You have a good night, I think I hear a nice, uncomplicated book calling my name. :-)
And thanks again for the tip, I'm going to Vegas on Tuesday so this will help me tremendously.
There might as well be some useful math on this thread. ;-)
Works the other way, too, if you ever need to multiply something by 5 (like sales tax). Just move the decimal and take half.
Yes. That is what I am saying.
PEMDAS (parenthesis, exponents, multiplication, division, addition, subtraction)are the order of operations.
I feel like I am a pro at it. We have four kids and I have helped all four of them with this.
We’re getting closer to the magic number of 1010011010 posts in this thread. Just a few more revelatory followups to go...
Fine but you all still did not make a complete change by adding the second set of parenthesis. Now I wash my hands of this mess of interpretative gobbledigoop.
Asked 5 different people in two states today to solve the problem and all without using any calculators said 2.
An extra set of parentheses is required only for those who don’t know about the distributive property and those who program computers.
Those who know of the existence of the distributive property can easily determine the only correct answer is 2.
And BTW, I was taught that multiplications should be done prior to division, but that was a long time ago.
LOL. We didn’t invent the rules—we’re just following them.
I guess PEMDAS is easier to remember than PEIMIDAS.
So you ask 5 different people in two stated. So 5*2 =10 people.
That is exactly right and why the correct answer can only be 2.
"Your math problem is too ambiguous and needs to be re-written for clarification."
Ambiguous? There's only one possible meaning that's consistent with the rules of arithmetic. That's to obtain 288 as you did. The only way to produce the answer "2" is to insert an additional set of parenthesis that changes the factor that the division operator operates on from "2" to "2*12". There is no /(2(12)), it is only imagined in error.
In the original equation there are 3 factors, which are 48, 1/2 and 12. There is no factor of "2" in the equation. the equation is 48*1/2*12. Division is an inverse operation. There's a factor of 1/2, because the division operator means, "multiply by the multiplicative inverse of the following number". Arithmetic operators do not act beyond the single number, or value which follows them. They never span another operator and the number that operator acts on, so to imagine parenthesis that cause such an extension is an error, not an example of ambiguity.
When I first posted (somewhere in the 300s)I said the correct answer was 2. Then I did what you did and rewrote the equation as 48*1/2*12 and determined my first answer was incorrect and the answer is 288.
Agree completely, and further to the point, a word processor created text paragraph makes matters so much worse. Written with a pencil on a blank piece of paper, the equation would have been more clear with or without the extra parens.
Using this logic, it'd be 48*1/2*1/12. Or 2. You would add the original 9+3, but is still in the denominator making it's absolute value 1/12.
I prefer the explanation in post 351.
Really? Well, maybe you can explain it to me. I no understand.
No, the division operator only effects the number immediately folling it. No operator extends beyond the number it precedes.
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