Math CentralQuandaries & Queries


Question from keith:

if a full reel of paper has 7750 metres on it with a diameter of 1240mm and a core diameter of 100mm how can work out the thickness of each strip of paper therefore allowing me to work out the metreage of the roll when its half in diametre at say 620mm

Hi Keith,

Look at my response to Toumas' question concerning a roll of paper. In it I showed that

\[t \times L = \pi (R^2 - r^2)\]

where $t$ is the thickness pf the paper, $L$ is the length of the paper on the roll, $R$ is the radius of the roll and $r$ is the radius of the core. All the dimensions need to be in the same units so if we use millimeters then you have $L = 7,750,000$ mm.

Use this formula to solve for $t.$

Write back if you need more help,

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