VinaOnline.net # Practice shapes vocabulary for math

### I. Count number of triangles

The classic example is that of the triangular “matchstick” configuration as shown below.

### The usual first step is simply to enumerate all of the distinct shape types of interest. Oftentimes, finding all of the shape types is the most tricky and potentially treacherous step—it can take some experience and meticulousness not to miss anything. Luckily, for this problem, it is relatively simple to enumerate all of the cases. Clearly, there are only three possible sizes of triangles: those having side length 1, side length 2, and side length 3.

The next step is to take a “census” of the different shape types. In this problem, it is fairly straightforward to do the census directly.

There are triangles of side length 1:

### There are  triangles of side length 2:

### Finally, there is only  triangle of side length 3:

### Thus, in total, there are triangles.

Post in the same topic: Shapes vocabulary for math

### II. Fill information

For each of the shapes below,

* Shade the parallel lines, using a different color for each pair;

* Write down the number of pairs of parallel lines;

* Mark in the right angles using a square. The first one is done for you.

### Number 1

* Slides: 4

* Right angles: 4

* Pairs of parallel lines: 2

Number 2-6?

### III. Identifying shapes

Name of shape: Rectangle, Triangle, Square, Circle, Parallelogram, Trapezoid (hoặc trapezium)

Sides: Rỗng, 3, 4.

Corners: Rỗng, 3, 4

Need to know:

+ All sides are the same length. The boxes on a checkerboard are square.

+ Yield signs are triangles, and a piece of bread can easily be cut into two triangles.

+ Stoplights are circles, and so are most dinner plates oval   It looks like a squashed circle.

+ It has two pairs of sides that are the same length. A ping-pong table is a rectangle.

+ Only one pair of sides is parallel, and the sides that are parallel aren’t the same length. If you cut the top off of a pyramid, you would have a trapezoid.

+ It’s like a rectangle that leaned over.

The rectangle is done for you.

Name of shape: Rectangle

Sides: 4

Corners: 4

Need to know: It has two pairs of sides that are the same length. A ping-pong table is a rectangle.