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Slide the Top

Part of the Polygons & Quadrilaterals section of Coddy's Geometry journey. Lesson 39 of 61.

Cut a right triangle off one end of a parallelogram and slide it to the other end. The pieces fit together into a rectangle with the same base and the same height, so the parallelogram has the same area as that rectangle.

$Parallelogram with base 10, slanted side 7 and the dashed height 6$

So the area of a parallelogram is base × height, where the height is the distance between the parallel sides, measured at right angles. It is not the slanted side. Here the base is 10 and the height is 6, so the area is 60. The slanted side 7 plays no part.

Challenge

The top side DC of parallelogram ABCD slides along its dashed line: drag D and C follows. Watch the area while the shape leans. Then press Check.

Try it yourself

$Drag the figure and watch$

Drag the figure and watch

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Polygons & Quadrilaterals

2Regular Polygons

Regular Polygons From an Angle to the Sides Inside a Regular Polygon Recap: Regular Polygons

5Rectangles, Rhombi, Squares

Rectangles The Diagonal of a Rectangle Rhombus Angles Squares Recap: Special Parallelograms

8Area of Parallelograms

Area of a Rectangle A Side from the AreaSlide the TopArea of a Parallelogram Recap: Parallelogram Area

11Polygon Chases

Parallel Sides in a Pentagon Marks, Not Looks Pentagon with x Regular Shapes Together Recap: Polygon Chases