Download Grade 5 lesson 2.4

GRADE 5 LESSON 2.4
Addition and subtraction number stories
Objective: to review the use of mathematical models to solve number stories
MATH MESSAGE
 Niko has $8.00. Does he have enough money to buy 3 fancy pencils for $1.98 each
and an eraser for $1.73?
 What is the total cost of the 3 pencils and the eraser?
 How did you find this information out? Write it in your ISN.
NUMBER SENTENCES
(WRITE THESE IN YOUR ISN)
 A true number sentence is a sentence in
which the relation symbols and operation
symbols combine to create a sentence
where both sides of the sentence are equal
to each other.
 A false number sentence has sides that are
not equal to each other.
 A number sentence that contains a variable
is called an OPEN number sentence.
 Open number sentences are neither true or
false. (they become true or false when we
replace the variable with a number.
4+5=9
4 + 5 = 31
4+5=x
4+5=9
RELATION & OPERATION SYMBOLS
(WRITE THESE IN YOUR ISN)
 Relation Symbols
 < means is less than
 > means is greater than
 = means is equal to
 Operation Symbols
 + means plus
 - means minus
 X or * means times
 / or ÷ means divided by
Number sentences MUST have a relation symbol.
Number sentences MUST also have an operation
symbol.
WHAT MAKES A GOOD PROBLEM SOLVER?
 A good problem solver is someone who has learned how to organize information
to find a solution when he or she is not sure how to get the correct answer.
 Learning many different ways to do many different types of problems gives you
the ability to organize information in many different ways.
 Find page 41 – Situation Diagrams
 Open your Student Reference Book to pages 242-243
 Read the four steps of the guide and determine the type of situation in the
problem. Is it – parts and total? Change to more? Change to less? Or is it a
comparison problem?
FIND MATH MASTERS PAGE 42
 In pairs or groups of 3, complete lesson 2.4 Math masters page 42, Using Open
number sentences.
 Remember, an Open Number Sentence uses a VARIABLE. You MUST have a letter
in place of an unknown number in your sentences.
 What letter do you choose? You CAN choose ANY letter. However, most people
choose a letter that represents what they are trying to find out. For example, if I
wanted to know how many tea bags fell into the Boston Harbor, I might use the
letter t. (Always use a lowercase letter for now.)
FURTHER PRACTICE
 Complete student workbook pages 37 and 38.
 You may need to use page 415. If you need a computational grid, feel free to get
yourself one.
 (a computational grid is grid paper!) We have it in whiteboard form as well.
GAME
 Name that Number (student reference book page 325)
HOMEWORK – ENRICHMENT –
EXTRA PRACTICE
 Page 43 Open Sentences and Number Stories is homework for this lesson.
 Please complete page 44 if you would like additional practice. – Using situation
diagrams.
 Enrichment for this lesson is page 45 – Writing open number sentences.