# Order of Operation: BOD-MAS Rule

Lesson Planning of Order of Operation: BOD-MAS Rule

Subject Mathematics

Students` Learning Outcomes

• Recognize BOD-MAS rule, using only parentheses ( ).
• Carry out combined operation using BOD-MAS rules.

Information for Teachers

B Bracket first

O Orders (i.e. Powers and Square Roots, etc)

D Division and

M Multiplication

S Subtraction

• Parentheses are used in math to show a part of math expression or equation that must be solved first, before any other calculation are done.

Material / Resources

Writing board, chalk / marker, duster, textbook

Introduction

• Introduce to the students that Math operations tell whether to add, subtract, multiply or divide, and parenthesis tell which operation is to be done first.

Write 3 + 2 x 4 = ————- on board.

What are we to do – how can there be two answers in Math?

Explain the rule that we do multiplication first, addition second.

Ask can I make 3 + 2 x 4 = 20? (True)

• Tell the students that we follow the order like;
• 1.      B brackets first
• 2.      O Orders (Powers and square roots etc.)
• 3.      D Division
• 4.      M Multiplication
• 6.      S Subtraction
• Explain to the students that;
• Parenthesis ( ), can be used in math to show which part of the math expression should be done first, i.e. 8 – 5 + 1 and 8 – (5 + 1). The only difference between these two expressions is the parentheses.
• Operation given in parenthesis should be solved first.

Development

Activity 1

• Tell the students that we do operation on numbers. We add, subtract, multiply divide, but what to do if we have more than one operation to do at a time?
• How do we solve this: 3 – 5 ÷ (1 + 4) =?
• Let`s put BOD-MAS into practice.
• Repeat the acronym with whole class i.e. ( ), of, ÷, x +, -.
• Write the following examples on the board and solve with the help of the students.
• Write first example on the board refers to the BOD-MAS rule and ask;

o   Do we have any (parenthesis) [no]

o   Do we have any order or powers? [no]

o   What to do first addition or division? [division]

• Similarly discuss all the examples on board with students.
• Write on the board and explaining (8 – 4) + 5 x 8
• Parenthesis come first, so 8 – 4 = 4.
• Replace in the expression with 4, where (8 – 4) was, so: 4 + 5 x 8.
• This contains addition and multiplication. Multiplication comes before addition, so 5 x 8 = 40. Replace 40 with 5 x 8 in the sentence.
• That leaves 4 + 40. Finally, add 4 + 40 = 44. Solve few more same examples on the board with the help of the students.
• Divide class in groups of four and distribute mathematical sentences written on paper pieces. Each group will get the required result by applying brackets, e.g.

• Groups will swap their sheets after completing for the peer checking.

Activity 3

• Divide class into pairs
• Write numbers from 2-9 on paper slips fold them and put them in a box.
• Ask each pair to take one paper slip.
• Give them instruction that they have to use the number and operations to get the answer equal to 1.
• For example if they have got 4, they have to use 4 four times and get answer equal to 1 like ;( 4 ÷ 4) + 4 – 4 = 1
• Similarly find an expression to make the number equal to 0.
• Time the activity.
• If students don`t get the answers. Solve on the board with the help of the students.
• This will give them extensive practice with application of BOD-MAS.

Sum up / Conclusion

• Parentheses are used to show what should be done first in arithmetic expression.
• Parenthesis () are the most frequently used group symbols.

Assessment

• Give the following questions to solve individually.

1. 