Finding the value of the unknown

Subject:                               Mathematics

Grade:                  5                              Duration: 60 mins 

Strand:                                 Algebra

Sub-title:             Algebraic sentences

Focus Question:               How do I write and interpret expressions involving variables?

Attainment Target:

Employ algebraic reasoning through the use of expressions, equations and formulae to interpret, model and solve problems involving unknown quantities

Benchmark

 Use operation symbols to complete number sentences; identify the order of operations given algebraic expressions.

Key Skills

Investigate order of operations, Use algebraic sentences, Use variables, Use symbols, Identify variables, Form expressions, Work in groups, Operate electronic devices, solve number sentences

Key Vocabulary/ Concepts

Algebra/algebraic, Expression, Variable, N-sentence/Statement

Resources/Materials

Sets of cards with word expressions and matching algebraic expressions  Cards with numbers/symbols, Journal  / “Math kit”, Computer and any other available technologies, Speakers

Content Summary
An expression is a written or numeric statement.  Order of operations refers to the use and application of the four numeric operations i.e. addition, subtraction, multiplication and division


Day 1 
At the end of the lesson students should be able to:

1.       Investigate the order of operations when evaluating algebraic expressions

Engage

Students will

think of a whole number and perform the following instructions:

add 7 to the number, Double the answer,  Subtract 4, Divide the number by 2, Subtract the original number

Teacher will reveal a card on which 5 (the number students are expected to obtain) was already written. after displaying the number teacher will engage students in a discussion to determine how the teacher was able to guess the correct number

Explore

Students will

Use a letter to represent the rectangle (which represents the unknown number) and to write down the number of tiles/counters in each step.

Think of a number (N)  

Add 7 to it           n + 7

Double the answer         2(n + 7) =             2n + 14

Subtract 4                            (2n + 14) – 4

solve a variety of number sentences with missing numbers involving all four operations.    
From following examples you can learn How to Find The Value of an Algebraic Expression:-

Example 1 = Find the value of algebraic expression (p + q + r),
if (p = 1), (q = 2) and (r = 3)
Answer = The given algebraic expression is (p + q + r)
Put the respective values of (p = 1), (q = 2) and (r = 3) in the algebraic expression, and we get:
= 1 + 2 + 3
= 6
So The Value of the Given Algebraic Expression (p + q + r) is 6.

Example 2 = Find the value of algebraic expression (7x - 3y + 4),
if (x = 2) and (y = 3)
Answer = The given algebraic expression is (7x - 3y + 4)
Put the respective values of (x = 2) and (y = 3)in the algebraic expression, and we get:
= (7 X 2) - (3 X 3) + 4
Solve brackets and we get
= 14 - 9 + 4
Solve and we get:
= 9

So The Value of the Given Algebraic Expression (7x - 3y + 4) is 9.

Example 3 = Find the value of algebraic expression (8a ÷ 4b),
if (a = 2)and (b = 2)
Answer = The given algebraic expression is (8a ÷ 4b)
Put the respective values of (a = 2)and (b = 2) in the algebraic expression, and we get:
= (8 X 2) ÷ (4 X 2)
solve Brackets and we get:
= 16 ÷ 8
After division, we get:
= 2
So The Value of the Given Algebraic Expression (8a ÷ 4b) is 2

discuss how they arrived each response and the operation that was used to get there


view video on how to solve algebraic expressions and record information to share with class
https://youtu.be/uM-C0m_kDeE


Explain

Students will

Through demonstration, solve number sentences and share their understanding


Extend

Students will

investigate the order of operations when evaluating algebraic expressions.

try and solve this word problem: My granny is twice as old as my father. Last year my father was 38. How old is my granny?

work alongside teacher and group members to solve


Evaluate

Students will
complete the following