BODMAS question

Nov 2014
7
2
bikini bottom
In the rule of BODMAS

we have the DM rule

now which should I do first... is it Division or Multiplication?
Is it a "which comes first from the problem" starting on left?
 
Last edited by a moderator:
Oct 2014
27
10
Australia
It's the order in which it appears, the same with addition/subtraction
 

Hoempa

Math Team
Apr 2010
2,780
361
porknbeans said:
is it a "which comes first from the problem" starting on left?
Yes. Got it, or do you have some examples you doubt about?
 

Benit13

Math Team
Apr 2014
2,166
739
Glasgow
It actually doesn't matter which you do first for multiplication/division. The same is true also for addition/subtraction. The BODMAS rule is really

i) Brackets
ii) "of" (powers)
iii) division and multiplication
iv) addition and subtraction

For example:

\(\displaystyle 12 \times 5 \div 6\)

You could do:
\(\displaystyle 12 \times 5 = 60\)
\(\displaystyle 60 \div 6 = 10\)

but you might find it a bit easier to do the division first
\(\displaystyle 12 \div 6 = 2\)
\(\displaystyle 2 \times 5 = 10\)
 
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Nov 2014
7
2
bikini bottom
It actually doesn't matter which you do first for multiplication/division. The same is true also for addition/subtraction. The BODMAS rule is really

i) Brackets
ii) "of" (powers)
iii) division and multiplication
iv) addition and subtraction

For example:

\(\displaystyle 12 \times 5 \div 6\)

You could do:
\(\displaystyle 12 \times 5 = 60\)
\(\displaystyle 60 \div 6 = 10\)

but you might find it a bit easier to do the division first
\(\displaystyle 12 \div 6 = 2\)
\(\displaystyle 2 \times 5 = 10\)

yep this is the example that i need thanks :)
 

Hoempa

Math Team
Apr 2010
2,780
361
In addition,
Writing out a solution to Benit13's example, one finds \(\displaystyle 12 \times 5 \div 6 = 60 \div 6 = 10\).
To highlight the priority one may also add a step;
\(\displaystyle 12 \times 5 \div 6 = (12 \times 5) \div 6= 60 \div 6 = 10\)

Alternatively, to reduce the numbers, look for common divisors in the numerator and denominator by factoring (partly). Sort by multiplication and division and/or write as a fraction; first multiplications then divisions.
\(\displaystyle 12 \times 5 \div 6 =\frac{12\cdot 5}{6}= \frac{6\cdot 2 \cdot 5}{6} = 2 \cdot 5 = 10\)

This may avoid discussion about what the final answer would be, all expressions equal the final result.
 
Jul 2014
1,174
229
भारत
\(\displaystyle \begin{array}{|c|l|}
\hline
\textbf{B} & \textbf{B}\text{rackets first} \\
\hline
\textbf{O} & \textbf{O}\text{rders (ie Powers and Square Roots, etc.)} \\
\hline
\textbf{DM} & \textbf{D}\text{ivision and }\textbf{M}\text{ultiplication (left-to-right)} \\
\hline
\textbf{AS} & \textbf{A}\text{ddition and }\textbf{S}\text{ubtraction (left-to-right)} \\
\hline
\end{array}\)
 
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Jan 2014
392
71
The backwoods of Northern Ontario
It could also be done this way:

\(\displaystyle 12 \times 5 \div 6 =\)

\(\displaystyle 12 \times (5 \div 6) =\)

\(\displaystyle 12 \times \frac{5}{6}=\)

\(\displaystyle \frac {12 \times 5}{6}=\)

\(\displaystyle \frac {60}{6}=\)

\(\displaystyle 10\)
 
Jan 2020
2
0
US
I think, you should follow the order of the BODMAS rule. It means that first of all, you should solve brackets, after that you should divide, then you should multiply, then you should add and at last, you should subtract.
 

skeeter

Math Team
Jul 2011
3,292
1,776
Texas
I think, you should follow the order of the BODMAS rule. It means that first of all, you should solve brackets, after that you should divide, then you should multiply, then you should add and at last, you should subtract.
incorrect ... division is just multiplication by a reciprocal value, and subtraction is just addition of an opposite signed value. Post #2 is correct.