Part Disposal

Hi, I have a question regarding part disposals (looking at the questions in the BPP kit Part Disposal and Kutchen). In the Part Disposal question, the share goes from 70% to 35%, and when calculating the reduction in net assets, the total amount of the subsidiary's net assets is taken into account when arriving at the profit on disposal figure. However, in the Kutchen question, the share goes from 80% to 0%, and when calculating the reduction in net assets, only a share of the net assets is taken into account (80% of the total net assets). Can you explain why there's two different approachs?