Khan/khan-exercises — pull request #93413 by petercollingridge (2013-10-21 11:03:06+00:00)
Title: Change probabilities of questions for Multiplication 4

There's a 50-50 chance for the large number to be 3- or 4-digit number, and a 75% chance for the small number to be 2- rather than a 3-digit number.
For Trello card: https://trello.com/c/xIRtZRJH/339-multiplication-4