Mary B.

asked • 11/02/12

7+7/7+7x7-7

what is the answer? is it  50???

Imran Z.

Answer should be "Infinity"
 
Here is why
 
7 + 7 ÷ 7 + 7 X 7 -7
 
Can alse be written as
 
{(7 + 7) ÷ (7 + 7) X (7 -7)}
 
Start solving it from right to left
 
{(14) ÷ (14) X (0)}

Further right to left
 
{(14) ÷ (0)}
 
Finally:
 
Anything divided by zero is infinity so if 14 is divided by zero it would be "Infinity"
 
{(14) ÷ (0)} =  ∞
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03/12/15

Alyssa F.

You are breaking the rule for Order of Operations. PEDMAS - Parentheses Exponents Division Multiplication Addition Subtraction. No parentheses and no exponents means you start with Division. You can not randomly add parentheses if there are none. It changes the answer. Without parentheses, you solve multiplication and division first, left to right, then addition and subtraction, left to right. 7/7 and 7*7 should be done first. 7/7 = 1 and 7*7 = 49. Plug them back in and you have
 
7 + 1 + 49 - 7. 7+1 = 8. 8+49 = 57. 57- 7 = 50.
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03/13/15

Alyssa F.

Order of Operations - PEDMAS (Parentheses, Exponents, Division, Multiplication, Addition, Subtraction). If it's not there, you can't add them. You do 7/7 and 7*7 first, getting 1 and 49, respectively, then plug them back into the equation:
 
7 + 1 + 49 - 7. 

NEXT: Addition, then subtraction, left to right. 7 = 1 = 8. 8 +49 = 57. 57 - 7 = 50.
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03/13/15

Glen G.

7 + 7 ÷ 7 + 7 × 7 – 7
can also be written as
(7 + 7) ÷ (7 + 7) × (7 – 7)
which can then be simplified to...
14 ÷ 14 × 0
which when properly computed becomes...
14 ÷ 0
which is not a legal fraction, but is an expression of an undefined quantity.
Therefore, the correct answer is UNDEFINED.
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03/17/15

Alyssa F.

You can not put the parentheses there. You have to follow the order of operations: PEDMAS - Parentheses Exponents Division/Multiplication left to right, Addition/Subtraction left to right:
No parentheses, no exponents, so start with division and multiplication L to R: 7/7 (1) and 7 x 7 (49)
So, you then have 7 + 1 + 49 - 7. Now you do additiona nd subtraction L to R: 7 + 1 = 8. 8 + 49 = 57. 57 - 7 = 50.
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03/17/15

Alyssa F.

Incorrect. The division is separated from the multiplication by an addition sign. The problem is 7 + 7/7 + 7x7 - 7.
 
STEP 1: In the absense of parentheses or exponents, do the multiplication, So, the problem then becomes 7 + 7/7 + 49-7.
STEP 2: Division. You then have 7 + 1 + 49 - 7.
STEP 3: Addition. 7 + 1 + 49 = 57. So now you have 57 - 7.
STEP 4: Subtraction. 57 - 7 = 50.

BTW, it's not Multiplication, then Division. It's Multiplication OR Division, LEFT TO RIGHT. Same goes for Addition and Subtraction. It's not Addition THEN subtraction. It's Addition OR subtraction, LEFT TO RIGHT. In this problem, it wouldn't make any difference whether you did the division or multiplication first, as there is an addition sign separating the two. Were that NOT the case, the division would come first, as it's before the multiplication, going left to right. I have been working with a Fifth Grader on this recently. 
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03/19/15

James C.

Why wouldn't this work?
7+7=14
14/7=2
2+7=9
9x7=63
63-7=56  ?
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03/21/15

Bill P.

Actually, given an equation as was first presented:  7 + 7 / 7 + 7 x 7 - 7  , it is NEVER allowed that you can rewrite the equation as: {(7 + 7) / (7 + 7) x (7 - 7)}  There is NO ambiguity in the original equation.  Our understanding of mathematics leaves no room in the least to interpret the equation in any way other than to arrive at 50 as a resolution. We may pencil in parentheses if we wish (as a visual aid), so long as they adhere to the laws of mathematics. Remember, no person in the history of humanity (or in all of ANY history) ever invented anything at all to do with mathematics.  We have simply "discovered" things about mathematics.  Mathematics simply IS.  And each and every aspect of mathematics that we do not yet know and may someday discover, exists today and simply IS.
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03/22/15

Laura L.

The solution - the ONLY solution - is 50 because you must always follow the rule of precedence of operations (aka Order of Operations).

There are no brackets, there are no exponents... so we continue to multiplication or division from left to right, and finally addition or subtraction from left to right.

It is easier to see of you first group per order of operations.

7+(7÷7)+(7*7)-7 <<<order of ops, 4th grade math
=7+1+49-7 <<<<second grade math
=50
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04/07/15

Paula S.

The actual answer is 56
7+7=14, then 14 divided by 7=2, then 2+7=9, then 9x7=63, then 63-7=56
Heck, it doesn't take a mathematician to add, divide, add, multiply and Subtract. Try it, you can Do It!!!! Simple math people ??
 
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04/15/15

Alyssa F.

Paula - the rules of mathematics have an order of operations (ones you have to do before you do any others). There is an acronym for it:PEDMAS - Parentheses, Exponents, Division, Multiplication, Addition, Subtraction. According to that rule, you have to do the 7/7 and 7x7 before you do the addition and subtraction. Therefore, following those laws, the equation would progress from 7 + 7/7 + 7x7 - 7 to 7 + 1 + 49 - 7. Then, 8 + 42, which equals 50.
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04/16/15

Manish J.

Perfect explanation by Alyssa. Just at the end instead of 8 + 42 it should be 57 - 7, which equals to 50 according to PEDMAS which is also known as BODMAS (Bracket, Operation, Division, Multiplication, Addition, Subtraction). Thnaks!
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06/19/15

Christopher R.

One starts with doing all the multiplication and divisions from left to right in, and then do all the additions and subtraction from left to right in which is:
 
7+7÷7+7×7-7=7+1+49-7=8+42=50
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06/20/15

Jacob K.

P
E
what ever comes first from left to right
M or d
A or s
7+7/7+7•7-7
7 / 7
7+1+7•7-7
7•7=49
7+1+49-1
7+1= 8
8+49-1
57-1

A=56
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06/27/15

Alyssa F.

Jacob - you changed the last 7 in the equation to a 1 in your 5th step, which changes the answer to 50, not 56. It should read 7+1+49-7, not 7+1+49-1. From there, it would be 8+49-7, then 57 - 7= 50. 
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06/27/15

Richard M.

All I will say is its not an equation without = its called an expression! 
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12/17/16

3 Answers By Expert Tutors

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Tamara J. answered • 11/02/12

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     7 + 7/7 + 7*7 - 7

First, you want to perform any division and/or multiplication operations. 

That is,     7/7 = 1      and      7*7 = 49 .

Then plug these answers into the original equation. 

     7 + 7/7 + 7*7 - 7  =  7 + 1 + 49 - 7 

Then you perform the addition and/or subtraction operations.

Notice that there is a +7 and -7 in the equation, which would cancel each other out (i.e., 7 - 7 = 0). So you would be left with the following:

        1 + 49 = 50 

Or, perform the operations in the order they are in:

      7 + 1 + 49 - 7 = 8 + 49 - 7 = 57 - 7 = 50 

Thus, the answer is 50 as you found yourself.

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Alyssa F. answered • 11/02/12

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Order of Operations says multiplaction adn division MUST be done first. Let's put parentheses ( ) around the division and multiplication to make it easier to see: 7 + (7/7) + (7x7) - 7. Now it should be easy to solve! 7/7 = 1. 7 x 7 = 49. Sub those back in and you have 7 + 1 + 49 - 7.  Now, since it's only + and -, the order of operations is unimportant, so the problem can be rearranged with the 7's together, like so: 7 - 7 + 1 + 49. Therefore, the answer is indeed 50. good job! :-)

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Jerry E.

Alyssa F said: "since it's only + and -, the order of operations is unimportant"
 
This would be true if the operations were all addition; however, it does not always hold when subtraction is involved. Consider the following examples:
 
(3-2)-1 = 0
3-(2-1) = 2
 
(3-2)+1 = 2
3-(2+1) = 0
 
In the absence of parentheses, the arithmetical rules are that operations with the same precedence (i.e., multiplication and division, or addition and subtraction) be performed left-to-right.
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05/27/14

Aaron K.

Actually, with + and - there is no need to go left to right, so long as you remember to group the operator with the number.
 
In your case, you have
+3, -2 and -1
It doesn't matter which order these are preformed.
-2-1 = -3
you forgot to bring the negative with the two in your second example.
 
-(2-1) expanded is not -2-1 as it is in the equation above, but is equal to -2+1
-2+1 = -(2-1)
So, for your first equation
3-2-1 = 0
-2-1+3 = 0
-1+3-2 = 0
Order is not important with addition and subtraction, however, the operator associated with the number is.
So, to reiterate,
3-2-1 =! 3-(2-1)
(=! Means does NOT equal)
 
The second equation has the same problem.
3-2+1 = 2
3+1-2 = 2
1-2+3 = 2
-2+1+3=2
If you are going to expand or contract equations, please do it properly.
3-(2+1) = 3-2-1 (you took out a factor of -1 from the 2-1 to make it -1(2+1) leaving the equation unbalanced)
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03/11/15

Alyssa F.

My mistake. I forgot the Order of Operations. It still equals 50, though.
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03/13/15

James C.

I apologize! And stand corrected 
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03/21/15

Olivia P. answered • 05/06/15

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50
The convention is: PEMDAS left to right.
However, multiplication and division are of equal rank, because division is just a form of multiplication. The same logic goes for addition and subtraction: they are of equal rank, because subtraction is just negative addition.

So:
7+ 1 + 49 -7 = 50
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