This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
for 289 I took the last element 9 and multiplied with the remaining
for 456 I took the first element 4 and multiplied with the remaining
for 748 I took the middle element and multiplied with the remaining
so for 387 i again took the last element
Its just my very random guess and I am not sure if this is the solution.