Math Q - Order of Ops (from MUS Alg 1)

[Parrothead]

Page 2A problem 8

 

In the video Mr. D said the order of operation is: parentheses, exponents, multiply, divide, add, subtract.

 

The problem reads: 18 divided by 2 times 5 plus 6.

 

Dd did the 2x5=10, 18/10=1.8, then added the 6 for 7.8

 

The answer in the book says the answer is 51 by dividing 18 by 2 then multiplying the 9 by 5 and adding 6.

 

What say the Hive? And if one is to divide first in that problem (after the instructions clearly state to multiply before dividing) how do I explain it do dd?

[Luckymama]

Parentheses

Exponents

Multiply or divide, whichever comes first as you go left to right in the problem

Add or subtract, again whichever comes first

[bbmom]

Multiply and divide (and addition and subtraction) are actually the same step, not different ones, so they go from left to right as you encounter them.

[Dana]

Parentheses

Exponents

Multiply or divide, whichever comes first as you go left to right in the problem

Add or subtract, again whichever comes first

 

:iagree:

 

Mult and div are equivalent operations and whichever come first is done first.

[tabrizia]

The order of operations is actually parentheses, exponents, multiply/divide, add/subtract.

 

So you do both multiplication and division left to right at the same time, same with addition and subtraction.

 

For instance 6 - 3 + 5 = 8 not -2. Multiply and divide are done at the same time, as are addition and subtraction. It can be a bit confusing when it isn't explained though and you just get the list of order of operations.

[Trez]

I believe the rule (better stated) is

brackets,

exponents,

multiply/divide,

add/subtract

 

The mult/divide and add/subtract are done left to right if there are more than one.

[MIch elle]

This website explains it: http://www.algebrahelp.com/lessons/simplifying/oops/

[nukeswife]

Check out this website for an explanation. http://www.purplemath.com/modules/orderops.htm

 

Basically Mult and Div are the same "Rank" In order of operations, so you do any multiplication or division before addition and subtraction, but also do whatever one comes first when going left to right.

 

So because the Div comes first when reading the problem left to right, you do that before the multiplication.

 

I know it can be confusing if they don't make it clear that M and D are really the same step in the order. The same goes for Add/Subt, you do which ever comes first when going left to right even thought the abbreviation says PEMDAS.

[Parrothead]

Okay. Thanks. It has been over 30 years since I did algebra and so I've forgotten most of it. And the explanation wasn't clear that m/d are equal and to go left to right. We both missed it.

[justasque]

Please

Excuse

(My Dear)

(Aunt Sally)

 

Parenthesis

Exponents

(Mulitiplication and Division)

(Addition and Subtraction)

 

PE(MD)(AS) <-- You can encourage the student to write it this way, at the top of their work page, as a reminder of the order.

[Pretty in Pink]

Please

Excuse

(My Dear)

(Aunt Sally)

 

Parenthesis

Exponents

(Mulitiplication and Division)

(Addition and Subtraction)

 

PE(MD)(AS) <-- You can encourage the student to write it this way, at the top of their work page, as a reminder of the order.

 

I'd forgotten all about that one. Thanks! I'll share it with my kiddos.