This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
The problem must be in the "NumberUtil.divideBigDecimal()" routine, or the "irDetail.getSentToPrQty()" or "part.getUomConversion()" methods aren't returning what you think they are. The solution you've been given is correct; running the following code gives "2" as the final answer: