[tex]\begin{gathered} \text{Divide the tons of fuel by the rate of fuelling} \\ \frac{12.40\text{ tons}}{0.2\text{ tons/min}}=62\text{ mins, (the tons cancel out)} \\ \text{It took them 62 mins to fuel the 12.40 tons of fuel} \\ 62\text{ mins}\rightarrow60\text{ mins}+2\text{ mins}\rightarrow1\text{ hour and 2 mins} \\ \text{Since they finished by 10:35, subtract it by 1 hour and 2 mins} \\ 10-1=9\text{ hours} \\ 35-2=33\text{ mins} \\ \text{Therefore, they started fuelling at 9:33 am.} \end{gathered}[/tex]
