This task is about finding the missing numbers that make up to ten or twenty.
Read the information and answer the following questions.
Task administration:
This task can be completed with pencil and paper or online (with auto marking displayed to students).
While the task is focusing on basic facts, students may use strategies to work out their answer. This can then help to identify students' ability to use strategies for addition tasks.
While the task is focusing on basic facts, students may use strategies to work out their answer. This can then help to identify students' ability to use strategies for addition tasks
Teaching and learning:
Students could solve these equations in a number of ways - by counting on, counting back (Stage 4: Advanced counting - strategy, from The Number Framework, book 1, 2004) or by simply recalling them as addition and subtraction facts (addition facts to 20 is at Stage 5: Early additive - knowledge).
Diagnostic and formative information:
Common error
Likely calculation
Likely misconception
a) i)
a) ii)
a) iii)
13
14
18
7 + 13 = 20
6 + 14 = 20
2 + 18 = 20
Finds the number that adds to 20 rather than 10.
a) i)
a) iii)
1
6
9 + 1 = 10
4 + 6 = 10
Finds the number that adds to 10 rather than 20.
a) ii)
a) ii)
6
12
Repeats given number.
Misinterprets question.
Next steps:
Once students are comfortable and confident with equations that total to twenty and are calculating without materials or pictures, get them to solve similar problems that total to 50. Encourage students to use an algebraic approach to solving these types of problems. Get them to record the word problems as equations with a missing number, i.e., 8 + _____ = 20.
