It took an earthquake to convince one city to do away with a double-decker highway. City planners in San Francisco had tried for years to get approval for removing the Embarcadero Freeway that blocked ...

Picture a bridge made of Legos. One side has three support pieces, the other two. How would you stabilize the bridge? Most people would add a piece so that there are three supports on each side, a new ...

Most adults learned to ride a bike in childhood by first plugging along on tricycles, then wobbling around on bikes with training wheels. Thanks to Ryan McFarland, our kids have it better. In 2007, ...

Subtraction is taking away one number from another. Lilly has 4 balloons, but then one flys away. How many does she have left? You can use subtraction to find the answer. First there were 4 balloons.