What is 5-5x5+5?

ianh said:
Following BODMAS the answer should be -25 as BODMAS has to be done in that order. However many folks on here are doing BODMSA instead to end up with -15 although there is the claim that you don't have to stick to AS order you just have to go left to right with AS which would mean using either AS or SA :D

Anyway,

5-5x5+5 = ?

5-(5x5)+5 = MULTIPLY FIRST - BODMAS

5-(25+5) = ADDITION SECOND - BODMAS

5-30 = SUBTRACTION LAST - BODMAS

or

5-(5x5)+5 = MULTIPLY FIRST - BODMSA

(5-25)+5 = SUBTRACTION SECOND - BODMSA

-20 + 5 = ADDITION LAST - BODMSA

Giving -25 or -15 but there's a few ways of doing it which will give different answers so, in the end, the real answer is the lessons we learnt on our journey to find the answer! :D
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Fairly sure you're joking, but the reason B.O.DM.AS gives equal precedence to Div/Multi, or Add/Subtract is simples.

The order you perform addition and subtraction doesn't matter. Similarly with div and multi.

+5 +5 -5
-5 +5 +5
+5 -5 +5

all the same answer (42).

10/2*4
4/2*10
1/2*10*4
e: correction, the above should read:
0.9999r/2*10*4

all the same answer (42).

5-5x5+5 is basically

+5 (-5x5) +5
+5 -(5x5) +5
-25 +5 +5
+5 +5 -25

all the same answer (42).
 
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Surprised so many didn't get this, as (unlike most of the numerous 'maths puzzles' floating around) there aren't any tricks with this question like putting similar looking images with different number of items etc.
 
ianh said:
5-(25+5) = ADDITION SECOND - BODMAS
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This line is wrong.

5-5×5+5 = 5-25+5

If you add 5, -25, and 5 together, you get -15. What you've done is change the latter part of the equation from -25+5 to -(25+5), which changes the sign of the second 5 and causes an incorrect answer.

5-25+5 ≠ 5-25-5
 
Division and multiplication have equal weight, as do addition and subtraction. Brackets are implied they would make for visual simplicity in this case. Most people would use brackets around the multiplication step when writing this down. The answer is not changed by the presence or absence of brackets.

The answer is definitely -15.
 
HangTime said:
Surprised so many didn't get this, as (unlike most of the numerous 'maths puzzles' floating around) there aren't any tricks with this question like putting similar looking images with different number of items etc.
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... you mean this treasure is one of the delights of facebook/twitter - do they put misinformation tags on wrong answers,

with the ternary opersator a question mark ? - it's evaluation is true.

name change for op ? if you can use symbols to this degree.
 
Hagar said:
There should be no need, I answered it in my head after reading the OP. Primary school math in the 1960's.
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For some reason he felt the need to make the same point no less than four times.

Bouton Aide said:
Don't tell OP the answer it will be fair their homework.

Google says -15.
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Bouton Aide said:
You don't need to work it out just google it.
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Bouton Aide said:
Yeh screw it just stick it into google.
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Bouton Aide said:
Why don't you just Google it. The answer is there or stick it in a calculator.
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What a mixed bag, the generation that came before mine. :rolleyes:
 
JohnG7 said:
In UK (maths not math) it would probably have brackets around part of it and we were taught to do that part first in school during the 70-80's.
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In the UK, just like anywhere else, it doesn't need brackets around it. It's obvious (from the rules) what it means.
Brackets would be used if the intent needed brackets, for example (5-5)x5+5. ie to prevent the rules from obscuring the intent.
 
Think most agree to do the multiplication first. All this order stuff about addition and subtraction is nonsense.

5-25+5 has only one answer. It's -15.

Anyone who thinks different needs to go back to school TBH!

If you wanna put brackets in there to make it clearer, you can also represent this as:
(5-25)+5
or
5-(25-5)

In the second case you gotta turn the +5 into a -5 to bring it into the brackets, as there's a minus sign in front of the brackets.
 
I was never taught bodmas, it was all about brackets.

So I look at it this way.

5-5x5+5

I start with five peas.

I take away five peas, that gives me no peas.

I multiply those no peas by five, I still have no peas.

Then I add five peas.

I end up with five peas.

Now can someone explain to me in simple terms how the answer can be anything different?
 
Feek said:
I was never taught bodmas, it was all about brackets.
Now can someone explain to me in simple terms how the answer can be anything different?
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It's the rules of mathematics. I don't mean to be flippant, dismissive or insulting, but it's literally because the rules of mathematics say so. There's nothing really to stop you from inventing your own maths system with your rules and then your method would be correct in that system, but in the maths system everyone else uses, the answer is -15 and always will be.
 
BOMDAS
Brackets then multiplication then division then addition then substraction.

So x first, and to get the multiplication do the 1st side on the left of it first. 5-5 =0
Then add the 5+5 to get the rhs of the multiplication - 5+5 =10
=
5-5 =(0) x 5 +5 (10)
= 0 x 10 = 0.
 
RxR said:
Brackets then multiplication then division then addition then substraction.

So x first
5-5 =0 x 5 +5 (10)
= 0 x 10 = 0.
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Despite the discussions above about how MDAS is not a strict order when dealing with MD and AS, you've managed to quote that you should do multiplication first and then.... not done the multiplication bit first? :confused: :p
 
nightwish said:
It's the rules of mathematics. I don't mean to be flippant, dismissive or insulting, but it's literally because the rules of mathematics say so. There's nothing really to stop you from inventing your own maths system with your rules and then your method would be correct in that system, but in the maths system everyone else uses, the answer is -15 and always will be.
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I have maths A level and genuinely, the first time I ever heard of this bodmas thing was on these forums.
 
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