Balancing the bank account

Balancing the bank account

Pencil and paperOnline interactive
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about solving equations and describing what the letters in them stand for.

Question 1Change answer

girl standing outside a bank
a)  On Monday, Amaia put $23 into her bank account, bringing her balance to $57.
      This equation shows the transaction:
y + 23 = 57
i)  What is the value of y? $ 
ii)  y stands for 
 

Question 1Change answer

b)  Here is another equation describing what Amaia did on Tuesday: 
57 - w = 49
i)   What is the value of w? $
ii)   What did she do on Tuesday? 

Question 1Change answer

c)  On Wednesday Amaia withdrew two lots of $x.
     The equation here shows this:  
49 - 2x = q
If x = $9, what was her final balance on Wednesday (q)? $
Task administration: 
This task is completed with pencil and paper or online with some auto-marking.
Level:
4
Curriculum info: 
Maths, Number and Algebra, Equations and expressions
Keywords: 
linear equations, money, pronumerals, substitution
Description of task: 
Students use linear equations to solve mathematical problems for money deposited and withdrawn from a bank account. They also identify parts of the related linear equation.
Learning Progression Frameworks
This resource can provide evidence of learning associated with
Using symbols and expressions to think mathematically, sets 4-5
within the Mathematics Learning Progressions Frameworks.
Read more about the Learning Progressions Frameworks.
Answers/responses: 
 

Y8 (04/1997)

Y9 (04/1997)
a) i)
ii)		 34
The balance before deposit on Monday.		 easy
difficult		 very easy
difficult
b) i)
ii)		 8
She took out $8 
or she took out money.		 easy
easy		 easy
very easy
c)   31 difficult moderate
Diagnostic and formative information: 
  Student response Likely calculation Likely misconception
a) ii) 34   Actual amount rather than what it stands for.
c) 20
40		 49 - 29
49 - 9		 Substitutes 9 into 2x as 29 rather than 2 × 9.
Subtracts 9 instead of multiplying by 2.