Kenken: Sudoku With Math

Kenken is a Sudoku variant invented by Tetsuya Miyamoto as a way to teach math. Frankly, Sudoku bores me senseless, but I found the addition of math makes the puzzles much more interesting.

The game is played on grids ranging from 4x4 to 9x9, and the rules are as follows:

• Do not repeat a number in any row or column.
• The numbers in each heavily outlined set of squares, called cages, must combine (in any order) to produce the target number in the top corner of the cage using the mathematical operation indicated.
• Cages with just one box should be filled in with the target number in the top corner.
• A number can be repeated within a cage as long as it is not in the same row or column.

Short version: the numbers you place in the bold boxes need to yield the number in the corner by multiplication, division, addition, or subtraction. 

Here's a video with Will Shortz (former editor of Games Magazine) explaining how to play.You can find playable puzzles at Kenken.com.