K J H.

asked • 01/21/17

What is the correct answer to this equation: 2 - 2 x 2 +1?

Would it be -1 or -3?

Andrew M.

Hello KJ,
 
The correct answer is -1. The mnemonic for order of operations is: PEMDAS.
PEMDAS: parentheses, exponents, multiplication/division, addition/subtraction.
Multiplication and division you do from left to right. Then you do addition and subtraction from left to write. Multiplication and addition are commutative and associative, meaning you can switch the order and grouping, so if you convert all of the divisions into multiplication of the reciprocals, you can do the multiplication in any order.
 
2-2x2+1 = 2+(-4)+1 = -2+1 = 2+(-3) = -1
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07/20/17

Sal B.

if there were a parentheses around the (2-2) then you would have to multiply the answer by 2 which would be 0x2=0, then add the 1=1. 
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01/02/18

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Andrew M. answered • 01/21/17

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Hello KJ.
 
Have you heard of the mnemonic PEMDAS? It tells you the order of operations:
Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction.
2-2*2+1 = 2-(2*2)+1 =2-4+1 = -1. You multiply and divide before you add or subtract.
Just out of curiosity, how do you get -3? 1 would be a common mistake.
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K J H.

Initially, I solved it correctly but wasn't sure it was correct. On my second attempt, it was a pure "WAG." After multiplying  - (2x2), I got -4.  I subtracted 2-2=0. Then, +1.  0-4+1= -3.  HAHA! Could I have been more wrong? Been out of school 45 yrs. DEFINITELY need to go bk. :) Thank you for your time.
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01/22/17

Andrew M.

It's great that you are exercising your brain. So, it looks like your goof was using the second 2 twice in your calculations. I can only hope that I will be exercising my brain 45 years removed from school. Best wishes.
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01/23/17

Dian M.

PEMDAS ? OK
2-2*2+1=?
2*2 =4 
2-4+1=?
4+1 = 5      Addition before substraction OK        
2-5 =-3
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07/19/17

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