How to improve math skills among American children

In the past two decades, researchers have made great strides in uncovering how children learn math, but little of that new knowledge has trickled down to teachers, according to a new book on math education.

Video: Why isn't weed killer working anymore?

Farmers used to worry about weeds. Then, herbicides solved that problem. At least for a while. In 1997, there were 432 new patents for herbicides; by 2009, there were only 65.

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