Tasks | Early Adolescence | Investigating Interger Operations

Tasks - Year 8

Investigating Interger Operations   by Thelma Perso, Senior Curriculum Officer, Mathematics

Phase of Development:   Early Adolescence

Learning Area/s:	Mathematics
Strand/s	Substrand/s
Number	Understand Numbers Understand Operations
Working Mathematically	Mathematical Strategies Apply and Verify
Expected Outcomes:	Students understand the difference between - as a subtraction operator and - when designating the opposite of.
Context:	I have used this investigation successfully with my year 8 students.
Learning Activities/ Experience:	The Graphics Calculator is a powerful tool for assisting students to understand the different roles of the - symbol in mathematics. Because there are two of these symbols on the graphics calculator students must choose which one to use in which context. I suggest students work in pairs so that their Working Mathematically strategies are enhanced
Resources:	Graphic Calculators Worksheet

Worksheet

Investigating Integer Operations

1. You will notice that your calculator has 2 - buttons : one of these is an operation button and the other has a place with the digits. What do you think this is for?

2. The (-) actually means the opposite of so the sequence (-) 4 enters the opposite of 4.

3. The - is the operator subtract or minus.

4. Investigate the results of the following (use a number line if you like so you can see what is happening).

NOTE: the (-) or the opposite of sign is written here as slightly above the centre, Eg. -4

5. Complete the following table using your calculator.

-2 + 5	-3 + 5	-1 + 5	-4 + 3	-6 + 10

By checking your answers using a number line, what do you think the (-), the opposite of symbol means?

6. Complete this table using your graphics calculator.

3 + -4	6 + -2	8 + -1	7 + -5	2 + -7

7. What seems to be happening here? Discuss your answers with your neighbour and write about what you have noticed.

8. Complete this table using your calculator.

6 - -1	3 - -2	8 - -7	12 - -4	6 - -8

9. What seems to be happening here? Discuss your answers with your neighbour and write about what you have noticed.

10. Now see if you can complete this table. Fill in the first column without using a calculator and then check them with your calculator afterwards.

	Solution	Calculator Check
6 - -1 6 + -4 7 - -3 -5 + 2 6 - -4 18 + -3 -7 + 12 -3 + -2 -6 - 9 -3 + -2 6½ + 8 3 - -1.5 8 + -7.2 -12 - -3 - 9 - -2 + 1 - 8 + -7 + 3