度量——長度

長度的度量，讀數和單位的轉換是其中的難點。至于長度的認識卻不是很難理解，所以這里不再展開。

讀數：
讀數的時候要注意兩種情況：
讀數的時候，人很容易只是注意後面的讀數，而忘記了量度的時候，開始並不是0，上面的圖顯示的是開始是0，所以讀數就是2厘米。
但是如果開始的值不是0，而是1的時候，筆尖對應的應該就是3厘米處，那麼很多學生讀數的時候就會認為這支筆的長度是3厘米。這就是忘記了開始不是0的情況。

Matchsticks

5、There are ten matchsticks lined up in 4 rows to form a shape as below. Only 3 matchsticks can be moved so that the shape becomes upside down.


Which 3 matchsticks should be moved?


Write down the number of the matchsticks in the squares of the new shape

Share oranges

3、serveral children are sharing some oranges, If each child takes 1 orange, there will be 1 orange remaining. However, if each child takes 2 oranges, then the last child will get nothin. How many children and oranges are there?
1) with equation:
Let n be the number of children:
n+1 = 2 (n -1)
n = 3

2)
First, give each child 1 orange. there 1 remaining, then give it to the first child.
Take the orange of the last child and give to the second child
Take the orange of the second last child and give to the third child....
so counting forwar, one more than half of children have 2 oranges, and the others have none. but there only one child got none. So the number of children is 2×1+1 = 3.