# Lesson Plan of BOD-MAS rule

#### Students’ Learning Outcomes

·         Recognize BOD MAS rule, using only parentheses ()
·         Carryout combined operations using BOD MAS rules.

#### Information for Teacher

BOD MAS: is a supportive abbreviation meaning brackets, order, division, multiplication, addition and subtraction, confirming that equation steps are completed in the correct order. A mathematical question with manifold operations may give different answers be liable on the order in which it is solved.

# Concept Map

#### Operations

·         “Operations” mean things like add, subtract, multiply, divide, squaring, etc. If it isn’t a number it is perhaps an operation.
·         But, when you see something like…
·         7 + (6 × 52 + 3)
·         … What part should you calculate first?
·         Start at the left and go to the right?
·         Or go from right to left?
·         Calculate them in the wrong order, and you will get a wrong answer!
·         So, long ago people agreed to follow rules when doing calculations, and they are:

#### Order of Operations

·         Do things in Brackets First
·         yes                         6 × (5 + 3)            =             6 × 8       =             48
·         not                         6 × (5 + 3)            =             30 + 3    =             33 (wrong
·         Exponents (Powers, Roots) before Multiply, Divide, Add or Subtract
·         yes                         5 × 22    =             5 × 4       =             20
·         not                         5 × 22    =             102         =             100 (wrong)
·         Multiply or Divide before you Add or Subtract
·         yes                         2 + 5 × 3                =             2 + 15    =  17
·         not                         2 + 5 × 3                =             7 × 3       =             21  (wrong)
·         Otherwise just go left to right
·         yes                         30 ÷ 5 × 3             =             6 × 3       =             1
·         not                         30 ÷ 5 × 3             =             30 ÷ 15 = 2          (wrong

#### How Do I Remember It All…? BOD MAS!

·         B: Brackets first
·         O: Order (i.e. Powers and Square Roots, etc.)
·         D: Division              (left to -to – right)
·         M: Multiplication  (left -to – right)
·         A: Addition            (left -to – right)
·         S: Subtraction       (left -to – right)
·         What about 7 + (6 × 52 + 3)?
·         7 + (6 × 52 + 3)
·         7 + (6 × 25 + 3)                   Start inside Brackets, and then use “Orders” First
·         7 + (150 + 3)                        Then Multiply
·         7 + (153)                               Then Add
·         7 + 153                 Brackets completed, last operation is add
·         160                         DONE!
·         Parentheses are used in math to show a part of a math expression or equation that must be solved first, before any other calculation are done.
·         In this lesson we will use only parentheses () as brackets.
·         While teaching the lesson, also consult textbook at all steps where and when applicable.

#### Material / Resources

Board, marker, textbook

#### Worm up activity

·         Introduce to the students that math operations tell whether to add, subtract, multiply or divide and parentheses 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:
·         Parentheses (), 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 parentheses should be solved first.

#### 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, +,-,
·         All is to do calculations in this order and solve the question.
·         Write following examples on the board and solve with help of the students:
 21 + 14 ÷ 7            = (21 + 2 = 23) (35 ÷ 7 = 5) (3 x 3  =9) (3 + – 6 = 2) 21 + 14 ÷ 7            = 3 x (5 – 2)              = 3 + 5 – (2 + 4)       =
·         Write first example on the board refer 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.

#### Activity 2

·         Write on the board and explaining (8 – 4) + 5 x 8
·         Parentheses 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. Sole few more same examples on the board with 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 2

·         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 like: ( 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

·         Parenthesis is used to show what should be done first in arithmetic expression.
·         Parenthesis ( ) are the most frequently used group symbol.

#### Assessment

·         Give the following questions to solve individually.