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Assessment Resource Centre (ARC)

  1. Stage 1
  2. Mathematics
  3. Activities
  4. Hidden number
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Hidden number

Grade Work Samples
End of Stage 1 (end of Year 2)
Grade A Bailey   Riley  
Grade B Bobby   Lee   Cameron  
Grade C Chris   Rania   Morgan  
Grade D Lesley   Pat  

Foundation Statement strands

The following strands are covered in this activity:

Working Mathematically, Number, Patterns and Algebra

Description of activity

Students supply a missing number in a number pattern on a hundreds chart and explain their reasoning.

  1. The teacher covers a number on a large hundreds chart.
  2. Students identify the number and record how the number was determined.
  3. They give six reasons for their answer.

The suggested time allocation for this activity is 30 minutes.

Suggested materials

A large hundreds chart or a chart on an overhead transparency, a cardboard square to cover a number on the chart, blank paper, pencils.

Prior learning

Students have had practice identifying, copying and continuing repeating patterns using shapes, objects, pictures and numbers that increase and decrease.

Students have an understanding of odd and even numbers, and are familiar with the terms ‘columns’ and ‘rows’ in relation to the hundreds chart.

Board of Studies NSW, Mathematics K–6 Syllabus, pp 42, 74
Board of Studies NSW, Mathematics K–6 Sample Units of Work, p 61


Whole Numbers (NS1.1)
Counts, orders, reads and represents two- and three-digit numbers
Patterns and Algebra (PAS1.1)
Creates, represents and continues a variety of number patterns, supplies missing elements in a pattern and builds number relationships
Applying Strategies (WMS1.2)
Uses objects, diagrams, imagery and technology to explore mathematical problems
Communicating (WMS1.3)
Describes mathematical situations and methods using everyday and some mathematical language, actions, materials, diagrams and symbols
Reasoning (WMS1.4)
Supports conclusions by explaining or demonstrating how answers were obtained

Criteria for assessing learning

Students will be assessed on their ability to:

  • identify a missing number in a pattern of numbers
  • describe a mathematical method using mathematical language, symbols and/or diagrams
  • explain how an answer was obtained

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