Number & Algebra
Chapter 3 | What's missing?
Teacher Resource Sheets
Getting Started
The mini sub trip (Getting started 3)
(Getting starting before page 85 to discuss the concept of tens numbers.)
- You could use this link to remind students how to use facts they know, e.g. 2 + 4 = 6, to solve problems with tens numbers, e.g. 2 tens + 4 tens = 6 tens or 60, and extend the pattern to solve 200 + ? = 600.
Jumping through tens numbers
What difference did the tide make? (Teacher Resource Sheet 9)
(After teaching section in conjunction with Activity 1, page 89. An example of a "change unknown" problem.)
- You could use this sheet to discuss how addition or subtraction can be used to calculate difference, and to help students find ways to record addition or subtraction, e.g. on a number line or using equations.
- Students may notice that the two equations suggested by Max and Jess belong to the same family of facts. If they don’t, then you may like to draw attention to this.
The crabs in the rock pool (Teacher Resource Sheet 10)
(After teaching section in conjunction with Activity 1, page 89. An example of a "change unknown" problem.)
- Students who are not fluent in their basic fact knowledge often find it difficult to decide what number needs to be added to reach a tens number. An abacus can substitute for tens frames and help struggling students identify how much is needed to make the next ten in numbers up to 100.
Using place value partitioning
Making the most of what we know (Teacher Resource Sheet 11)
(Help students who have difficulty understanding Max’s thinking on page 92. An example of a "change unknown" problem.)
- The discussion in the teaching section indicates the relationship between addition and subtraction, which is very important when deciding the most efficient strategy for finding difference.
- Saying “6 tens” rather 60, or 6 hundreds rather than 600, allows students to make a link to basic facts when adding or subtracting. Using place value equipment further cements this understanding.
Dolphin watch (Teacher Resource Sheet 12)
(Further discussion in conjunction with Activity 2, page 91. A word problems and suggests students use place value strategies to find the missing number of dolphins.)
- You could use part of the whole diagram to help students understand that the problem involves finding the difference between the part of the pod Jess can see and the whole.
- A picture of an abacus is included on the sheet. You may choose to draw student’s attention to this or provide other place value materials to support students who are having difficulty keeping track of tens and ones in a number.
Add or Subtract?
Lifeguards (Teacher Resource Sheet 13)
(Further discussion in conjunction with Activity 4, page 95. A sheet with a beach problem for discussion. Students are asked to convert a word problem with a part-part-whole diagram into an addition and a subtraction equation.)
- You can use the word problem and diagram to help students understand how both can be used to find the difference between two quantities.
- Once students have written the equation encourage them to use a strategy they know to solve the problem and then a different strategy to check their answers.
