Cutting the door down

Cutting the door down

Pencil and paper
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about millimetres, centimetres and metres.
Sharee bought a second hand door. The door was wider and taller than the door frame. The measurements shown in the diagrams below are all in millimetres.
 
 

 
a) How high is the door in metres? __________ m
 
b) How wide is the door in centimetres? __________ cm
 
c) Sharee wanted to cut the door so it was exactly the same size as the door frame. How many centimetres would she need to cut off the
 
  i) height of the door? __________ cm
 
  ii) width of the door? __________ cm
Task administration: 
This task can be completed with pencil and paper.
Level:
3
Curriculum info: 
Maths, Geometry and Measurement, Measurement
Keywords: 
length, conversion of units, metres, centimetres, millimetres
Description of task: 
Students convert the millimetre dimensions of a door to metres and centimetres.
Curriculum Links: 
This resource can help to identify students' understanding of converting between standard units of measurement for length.
Learning Progression Frameworks
This resource can provide evidence of learning associated with
Measurement sense, set 5
within the Mathematics Learning Progressions Frameworks.
Read more about the Learning Progressions Frameworks.
Answers/responses: 
   Y7 (03/1999)
a)    2 moderate
b)    68 moderate
c) i)
ii)		 2
3		 difficult
difficult
Diagnostic and formative information: 
  Common error Likely calculation Likely reason
a) 20
200
2000		    Assumes 1 m = 100 mm.
Assumes 1 m = 10 mm.
Answers in mm not m.
b) 6.8
200
3

(680 - 650)/10

 Assumes 100 mm = 1 cm.
Confuses height and width.
Calculates how much bigger the door is than the frame.
c) i)
    ii)		 20
30		    Answers in mm not cm.
c) i)
    ii)		 0.2
0.3		    Assumes 100 mm = 1 m.