5. Tractors need to have tyres of the correct size. All tyres have codes on them. The code on a tractor’s front tyre is 320/85R20. The ‘320’ means that the tyre is 320 mm wide.
(a) What is 320 mm in cm? [1]
(b)
A company that sells the tractor tyres stacks them one on top of each other. For safety reasons the piles are no more than 2 metres high. What is the greatest number of tyres that can be stacked safely in a single pile? [3]
Greatest number of tyres is ……………………
Mark scheme (a)
Scheme
Marks
Comments
Ribbon marking for 5(a) and 5(b) 32 (cm)
B1
Mark scheme (b)
Scheme
Marks
Comments
Ribbon marking for 5(a) and 5(b)
6 (tyres)
B3
FT ‘their 32’ from part (a)
This may be embedded in correct working. eg 6 × 32=192 (cm)
Award B2 for 200 ÷ 32 (cm) 2000 ÷ 320 (mm) 2 ÷ 0.32 (m) These workings may be seen as multiples eg 32 added up 6 times to 192.
Award B1 for 2 (m) ÷ 32 (cm) or 2000 (mm) ÷ 32 (cm) Or Sight of 200 cm Or Sight of 2000mm Or sight of 0.32m Or sight of working towards 200 or 2000 (eg working towards 192 or 1920) even with incorrect or mixed units
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