By 10, by 9, by 5, by 3, and by chunks. This unit contains tricks for multiplication and for checking your work. A playful (and very useful) approach to multiplication. This unit is presented at three levels of varying complexity.
"Cowboy Jake is afraid of rattlesnakes. He sees a lot of them on the ranch where he lives. In fact, he sees an average of thirty every year. About how many has he seen in the nine years he has lived on the ranch?"