How do you figure out math type Skill Testing Questions???

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Tue, Apr 17th, 2007, 02:00 AM
cndlady

How do you figure out math type Skill Testing Questions???

On another board I sometimes visit how to answer a skill testing question is always a controversy. So I am going to bring the controversy here and see if it can be solved by some of you very smart people :)

here is one particular question
100 + 40 / 2 =
now I would do this question from left to right like this:
(100 +40)/2 =70

on this other board one of the mods has stated that
Quote:
This ongoing debate is getting tiresome.

A lot of people discuss this as if there is more than one way you can solve an equation. There is only one mathematically CORRECT way.
If the sponsor accepts the wrong answer then they are being generous because they want to award the prize and are giving you extra leeway.

In the above example the only answer ANY math teacher in the world would mark as correct is 120.
If the sponsor tried to tell you the answer was wrong you would be able to prove that they made a mistake and they would have to apologize and award you the prize. If you answered the other way and they said you were wrong there would be nothing you could do because you WOULD be wrong.
This would mean that she did the question like this
100 + (40/2) = 120

I was taught in school that if the brackets weren't there you did a string from left to right...have things changed...do you put brackets in where they weren't???

I am hoping that one of you can solve this for me
Tue, Apr 17th, 2007, 02:15 AM
Boo Radley

being a "nerd" I feel offended when you argue that 100 + 40 / 2 = is the same as (100 +40)/2 =70 :razz:

This is mathematically wrong. It's like saying 1+1=3

Yes you go left to right but only for the same sign
e.g. 20 / 2 / 10 is the same as (20 / 2) / 10
note how i went from left to right in the above example

But when the signs are different things change!
Multiplication and division have higher priority to addition and subtration
e.g. 100 + 40 / 2
division has higher priority so
100 + (40 / 2)

To make things look uglier:
100 + 3 / 2 x 5 + 6 x 10 / 2
is the same as
100 + [ (3 / 2) x 5 ] + [ ( 6 x 10 ) / 2 ]

the conclusion is....

you should be thankful I don't get to write skill testing questions :lolsign:
Tue, Apr 17th, 2007, 02:19 AM
cndlady

well why the heck don't they put the brackets where they want them..
hmmm maybe that is why I don't win that many contests and things..
from now on I am making you do all my math questions for me
Tue, Apr 17th, 2007, 12:53 PM
2girlsmom

I hate math, and suck at it too.
Tue, Apr 17th, 2007, 01:27 PM
Boo Radley

Quote:

Originally Posted by cndlady

well why the heck don't they put the brackets where they want them..
hmmm maybe that is why I don't win that many contests and things..
from now on I am making you do all my math questions for me

coz it's supposed to be a "Skill Testing" question :wink:

sure :) just post the skill testing questions on here and I can help you out lol
Tue, Apr 17th, 2007, 01:29 PM
alajen

Oooh, oooh, I know this one. Had to rack my brain to remember. There is a convention for how to solve math equations, called Order of Operations. The way to remember is BEDMAS

B - Brackets
E - Exponents
D/M - Division and Multiplication
A/S - Addition and Subtraction

As Boo said, if there is more than one of the same group then you do them in order of left to right. Also, multiplication/division or addition/subtraction are commutative. Meaning, doesn't matter what order you do them if they are the SAME sign.

For example
2*3*5 = 30 or 5*2*3 = 30
OR 4+5+8 = 17 or 8+4+5 = 17

But NOT 4*3/6 = 2 or 6*4/3 = 8, because there are mixed signs

Unfortunately, the contest writers sometimes forget the convention, hence the confusing skill-testing questions. :confused2:
Tue, Apr 17th, 2007, 01:40 PM
momg

i had one that was really confusing i did really well in math at school and i know about the bracket thing but this one was really messed up i wish i could remember it
Tue, Apr 17th, 2007, 02:02 PM
Prue

Quote:

Originally Posted by alajen

Oooh, oooh, I know this one. Had to rack my brain to remember. There is a convention for how to solve math equations, called Order of Operations. The way to remember is BEDMAS

Thank you! I knew the rules, but I completely forgot the term BEDMAS! I was trying to think of it yesterday but it just would not come to me....and I was too tired to actually Google it! ;)
Tue, Apr 17th, 2007, 07:52 PM
Pinklicious

Oh, forget all that complicated stuff. Just do what I do:
Pull out your trusty calculator and punch in the question. Voila! Instant Genius. :P
Tue, Apr 17th, 2007, 09:06 PM
dawnikus

Quote:

Originally Posted by alajen

Oooh, oooh, I know this one. Had to rack my brain to remember. There is a convention for how to solve math equations, called Order of Operations. The way to remember is BEDMAS

B - Brackets
E - Exponents
D/M - Division and Multiplication
A/S - Addition and Subtraction

As Boo said, if there is more than one of the same group then you do them in order of left to right. Also, multiplication/division or addition/subtraction are commutative. Meaning, doesn't matter what order you do them if they are the SAME sign.

For example
2*3*5 = 30 or 5*2*3 = 30
OR 4+5+8 = 17 or 8+4+5 = 17

But NOT 4*3/6 = 2 or 6*4/3 = 8, because there are mixed signs

Unfortunately, the contest writers sometimes forget the convention, hence the confusing skill-testing questions. :confused2:

Well said on the bedmas issue. :)
Tue, Apr 17th, 2007, 11:41 PM
cndlady

bcteagirl sent me this addy really explains it well
http://www.mathgoodies.com/lessons/v...perations.html
Wed, Apr 18th, 2007, 12:17 AM
IreneWpg

Whoa....have I ever been taken down a peg or three!!

I have been doing the skill-testing questions and I would have bet I had them correct. I, like Cndlady worked from left to right giving preferene to parenthesis. For example 4 + 3 - 6 x 7 (divide sign) 6 = my answer would have been 1.1666666......You are telling me the answer is actually 0. Right? Are you sure? I would hae bet big bucks that I was right.

[I know it's been a while since I've been in school, but I don't ever recall doing things that way.]
Wed, Apr 18th, 2007, 12:19 AM
Prue

Yup it would be 0 :P
Wed, Apr 18th, 2007, 12:27 AM
bcteagirl

Yup... I remember having that order drilled into my head.
Wed, Apr 18th, 2007, 12:47 AM
IreneWpg

Well I have answered a lot of skill-testing questions wrong! It's no wonder I never won.

Are you sure? OK, I know you're probably right......I just can't believe I was so wrong. I don't know if I feel stupid or old.
Wed, Apr 18th, 2007, 01:35 AM
cndlady

Quote:

Originally Posted by irenewpg

Well I have answered a lot of skill-testing questions wrong! It's no wonder I never won.

Are you sure? OK, I know you're probably right......I just can't believe I was so wrong. I don't know if I feel stupid or old.

Math has sure changed since we went to school Irene..
Like I said I started this thread because it was a huge discussion on another board and since I figured we had the smartest people here I would ask them :)
Wed, Apr 18th, 2007, 10:06 AM
alajen

The math question always has a WHOLE number as the answer. No fractions. So if you get an answer with something after the decimal point, then look at the equation and try again :)
Wed, Apr 18th, 2007, 11:20 PM
IreneWpg

Quote:

Originally Posted by alajen

The math question always has a WHOLE number as the answer. No fractions. So if you get an answer with something after the decimal point, then look at the equation and try again :)

THAT I knew (I just gave a quick example with numbers off the top of my head).

I checked all the skill-testing questions today and....they are all pretty straight forward....no multiplication or division that are not in brackets. So, I guess I am back to just being plain unlucky when it comes to winning contests. It has nothing to do with my lack of mathamatical skills.