1. How many triangles are there?

2. How many triangles are there?

3. How many triangles are there?

http://www.allmathtricks.com/number-triangles/

4. How many triangles are there?

5. How many triangles are there?

6. How many rectangles(not including squares) can you see in the figure?

7. How many triangles are there?

8. How many triangles are there?

9. How many triangles are there? (Ignore the grids)

10. How many squares are there in all?

11. How many triangles are there?

https://brilliant.org/wiki/triangle-triage/

12. How many rectangles are there in the given figure?

Answers:

- 5
- 3
- 6
- 12
- 12
- 9
- 16
- 16
- 15
- 14
- 13
- 11

如果数不清, 那就画一画，可以试试用不同的颜色的笔。最好家长和小朋友一起数，就像玩游戏一样。

还有一个办法就是按照大小归类,然后加在一起,这样不容易出错. 比如第11题，

1. 边长为1格(最小的)的三角形有多少个: 9

2. 边长为2格的三角形有多少个: 3

3. 边长为3格(最大的)的三角形有多少个: 1

所以一共是13个