A trader has three different types of oils of volume $\displaystyle 870 l, 812 l$ and $\displaystyle 638 l$. Find the least number of containers of equal size required to store all the oil without getting mixed.

Least number of containers means maximum volume in each container. \[\begin{aligned} & 870=2 \times 3 \times 5 \times 29 \\ & 812=2^{2} \times 7 \times 29 \\ & 638=2 \times 11 \times 29 \\ & \therefore \text { H.C.F. }(870,812,638)=2 \times 29=58 \\ & \text { Number of containers of different types required }=\frac{870}{58}+\frac{812}{58}+\frac{638}{58} \\ & =15+14+11 \\ & =40 \end{aligned} \]