Justify the choice of referents for units in both the SI system and the Imperial system (e.g, the width of the thumb for an inch and the width of the little finger for 1 centimetre).

Estimate, using personal referents for SI and Imperial units, linear measurements such as the dimensions of regular 3-D objects or 2-D shapes found in the classroom, at home, or in the community.

Explain why and how the same linear measurement can be expressed using:

• equivalent SI units (e.g., 10 centimetres, 0.1 metres, and 100 millimetres)
• equivalent Imperial units (e.g., 6 inches, $1/2$ foot, $6/36$ or $1/6$ yard).

Measure and record (using Canadian spelling and abbreviations for SI or Imperial units) using a variety of instruments such as trundle or surveyor’s wheels, height gauges, metric and Imperial tapes and rulers, carpenter’s squares, micrometers, fractional or electronic callipers, and pedometers:

• distances at school, at home, and in the community
• inside diameters, outside diameters, lengths, and widths of personally relevant 3-D objects.

Develop, generalize, explain, and apply strategies to convert units of linear measurements within the same system (e.g., feet to yards, or metres to millimetres).

Apply knowledge and skills with linear measurement to create and solve or verify the reasonableness of solutions to situational questions relevant to self, family, or community (including perimeter, circumference, and the length + width + height measurement used in shipping and air travel).

Determine the operation that should be used to solve a linear measurement problem and explain the reasoning (e.g., Write the equation that could be used to determine how many lengths of $1/3$ of a yard can be cut out of a log measuring $5 1/2$ yards).

Develop, generalize, explain, and apply strategies to determine the midpoint of a linear measurement, such as the length, width, height, depth, diagonal length, or diameter of a 3-D object (e.g., A wall measures 5 yards and $6 7/8$ inches. If a painting is to be hung centered on the wall, how far is the centre of the painting from each of the adjacent walls?).

Critique the statement “the distance between Regina and Saskatoon is 2 hours”.