A scientist calculates that the thickness of a piece of paper is \( 1.09 \times 10^{-4} \mathrm{~m} \). Write this thickness as an ordinary number. Give your answer in metres \( (\mathrm{m}) \).

To express the thickness of the paper as an ordinary number, you simply move the decimal point four places to the right, since the exponent is \(-4\). This gives you \(0.000109\) meters. So, the thickness of the paper is \(0.000109 \, \text{m}\).