In this video, Zeke learns how to classify triangles by side length (equilateral, isosceles, scalene) and angle measurement (right, acute, and obtuse).

In this video, Marta learns various ways to subtract 2-digit numbers from 2-digit numbers, including regrouping and marking out.

Watch this video to learn about food chains. A food chain shows how energy moves from one living thing to another.

In this video, Emily and Carlos learn to solve math problems that have missing information by using a 2-step process of asking questions and then checking the answer.

In this video, Jackson learns to identify and label basic three-dimensional geometric shapes (cube, sphere, cone, cylinder) and compare them to flat geometric shapes.

Students learn about same and different signs in this video. When they have different signs the product is negative, while same signs means the product is positive.

Water covers more than 3/4 of Earth's surface. Watch this animation to learn about the water cycle and how the water cycle affects weather and climate.

In this video, Carlos learns how to use an organized list and tally marks to solve the problem of how many quarters, dimes and nickels he will need to buy an apple.

In this video, Jackson learns the properties of basic three-dimensional geometric shapes by selecting the best shapes (cube, sphere, cylinder, cone) and arranging them appropriately to build a tower.

In this video, Alex uses place-value blocks to learn how the 10s and 1s place digits increase or decrease as values are added or removed from 2-digit numbers.

Meet Matt Tavares, illustrator of Iron Hans: A Grimms' Fairy Tale, and learn about his collaboration for Lady Liberty in this video clip (2:02).