Crunch Machine

Purpose

This is a level 2 algebra strand activity from the Figure It Out series.
A PDF of the student activity is included.

Achievement Objectives
NA2-2: Know forward and backward counting sequences with whole numbers to at least 1000.
NA2-6: Communicate and interpret simple additive strategies, using words, diagrams (pictures), and symbols.
Student Activity

Click on the image to enlarge it. Click again to close. Download PDF (306 KB)

Specific Learning Outcomes

solve basic facts

select operation symbols ( +, -, x, ÷) to complete an equation

Required Resource Materials
calculator

FIO, Level 2-3, Algebra, Crunch Machine, page 17

classmate

Activity

Activity One

Organising the results in an in/out table may help students to recognise patterns:

Activity Two

Some students may need a calculator to help them, although processing the problems mentally is more efficient.
Realising that the = sign must go in one of the vacant squares is a clue to how the problems can be
solved in an organised way.
For example, question 3 offers three possibilities:
15 = 21  4  40 [This looks unlikely.]
15  21 = 4  40 [More likely, although + and – are the only likely operators.]
15  21  4 = 40 [Using addition signs gives the correct solution.]
Students may enjoy making up their own problems, although this is another case where creating
problems is much easier than solving them.

Activity One
+ 5
2 + 5 = 7
4 + 5 = 9
6 + 5 = 11
8 + 5 = 13
10 + 5 = 15

- 8
8 – 8 = 0
12 – 8 = 4
16 – 8 = 8
20 – 8 = 12

x 3
7 x 3 = 21
8 x 3 = 24
9 x 3 = 27
10 x 3 = 30

÷ 5
5 ÷ 5 = 1
10 ÷ 5 = 2
15 ÷ 5 = 3
20 ÷ 5 = 4

Activity Two
1. 6 ÷ 3 = 2 or 6 = 3 x 2
2. 50 = 10 + 10 + 30, 50 – 10 = 10 + 30, or 50 – 10 – 10 = 30
3. 15 + 21 + 4 = 40
4. 24 = 6 x 4 or 24 ÷ 6 = 4
5. 16 + 17 = 3 x 11
6. 10 = 2 x 3 + 4 or 10 + 2 = 3 x 4
7. 12 = 3 x 2 x 2 or 12 ÷ 3 = 2 x 2
8. 40 + 3 + 7 = 50

Activity Three