SOLUTION: The order of operations is used to solve the expression 6 + 42 ÷ 2 - 15 = 12 I thought the answer was 9 because I added 6 + 42 which is 48. Then I divided 48 by 2 which is

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Question 1204585: The order of operations is used to solve the expression
6 + 42 ÷ 2 - 15 = 12
I thought the answer was 9 because I added 6 + 42 which is 48. Then I divided 48 by 2 which is 24. I then subtracted 15 from 24 which is 9. I added first because I thought the PEMDAS was to be solved from left to right.
Found 5 solutions by MathLover1, Edwin McCravy, math_tutor2020, ikleyn, greenestamps:
Answer by MathLover1(20850)   (Show Source): You can put this solution on YOUR website!

The order is PEMDAS:
Parentheses,
Exponents,
Multiplication,
Division (from left to right),
Addition
Subtraction (from left to right)

you are given:


here you have no Parentheses,
Exponents,
Multiplication,

but you have division, so do that first

now you can add and subtract

proven that statement is true

Answer by Edwin McCravy(20059)   (Show Source): You can put this solution on YOUR website!
Then please re-learn PEMDAS.  And, be sure to learn that there are two flaws in
it.
  
P
It says to complete first what's inside any parentheses "( )", 
until what's inside them becomes a single number, then erase the parentheses and
write it as a single number.

Then do the same with brackets "[ ]".
Then do the same with braces "{ }".

E
Then complete any exponents.

MD
Then go from left to right, and when you come to either a multiplication or
division, whichever comes first, going left to right, complete it and replace it
by a single number. 

AS
Then go from left to right, and when you come to either an addition or
subtraction, whichever comes first, going left to right, complete it and replace
it by a single number.

FLAWS
The first flaw of PEMDAS is that the "MD" misleads some people to believe
multiplication always comes before division, which is false, because it's
whichever comes first going left to right.

The second flaw is similar. the "AS" misleads some people to believe addition
always comes before subtraction, which is false, because, like multiplication
and division, it's whichever comes first going left to right.  

Be sure to do the M's and D's before doing the A's and S's. J

Edwin
Answer by math_tutor2020(3817)   (Show Source): You can put this solution on YOUR website!

There's not much to mention that hasn't been said by the other tutors.

However, let's focus on the 6 + 42 ÷ 2 portion.

That is of the template A + B
A = 6
B = 42 ÷ 2

Recall that we can add two numbers in any order.
Example: 2+3 = 5 and 3+2 = 5

So the A + B is the same as B + A, which means 6 + 42 ÷ 2 flips to 42 ÷ 2 + 6

This might help show you that the 42 ÷ 2 portion is the first thing to be evaluated.
Answer by ikleyn(52798)   (Show Source): You can put this solution on YOUR website!
.
The order of operations is used to solve the expression

6 + 42 ÷ 2 - 15 = 12

I thought the answer was 9 because I added 6 + 42 which is 48. Then I divided 48 by 2 which is 24.
I then subtracted 15 from 24 which is 9. I added first because I thought the PEMDAS was to be solved from left to right.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Your difficulties started from the fact, that you incorrectly understood the problem.

In part, you incorrectly understood the problem, because its formulation is fault (defective).


The correctly posed question should sound this way

        "Place parentheses in order for the given expression be a valid equality".


Having a correctly formulated problem, its solution is (usually)
much easier (and has much more sense) than a solution to a problem, posed incorrectly.


In a way, how the problem is posed in the post, there is no doubt
that it originates from some trash bin.


In more accurate terms, there is no doubt that it originates from an untrusted source.



Answer by greenestamps(13200)   (Show Source): You can put this solution on YOUR website!


Tutor @ikleyn has again tried to show her superiority by posting a response that says the problem should have been to insert parentheses so that the given statement was true.

That is absolute hogwash -- as are many of her posts where she tries to correct the statement of the problem, or to disparage the responses from other tutors.

There is no need to add any parentheses to make the given statement true.

Standard order of operations means you do the multiplications and/or divisions before you do the additions and/or subtractions.

So the first operation in the expression on the left is 42/2, which is 21.

After that, the expression is 6+21-15, which is equal to 12 -- so the statement as posted is correct.

There is no need for adding parentheses...
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