Here's a NumberWiz problem, where I've replaced the Big numbers with numbers of my own choice. In this case I've replaced 25, 50, 75 and 100 with 31, 51, 69 and 85.
And now the problem is:
How do you add, subtract, multiply and divide 6 9 10 51 69 85 to get 888?
Would be nice to see a solution in the comments.
This example illustrates the new feature in NumberWiz v2.0.
You can buy NumberWiz for $1.99 in the App Store and enjoy many more of these problems.