Overview: 7 questions will be solved this time.Among them
           ☆7 integer calculations

[1/7 Integer column vertical calculation]
    Question type: Integer multiplication
    Original question: 21×2
    Solution:
    21×2 = 42
    Column vertical calculation:

						2	1
✖							2
						4	2
						4	2

[2/7 Integer column vertical calculation]
    Question type: Integer multiplication
    Original question: 41×2
    Solution:
    41×2 = 82
    Column vertical calculation:

						4	1
✖							2
						8	2
						8	2

[3/7 Integer column vertical calculation]
    Question type: Integer multiplication
    Original question: 40×4
    Solution:
    40×4 = 160
    Column vertical calculation:

						4	0
✖							4
					1	6	0
					1	6	0

[4/7 Integer column vertical calculation]
    Question type: Integer multiplication
    Original question: 14×4
    Solution:
    14×4 = 56
    Column vertical calculation:

						1	4
✖							4
						5	6
						5	6

[5/7 Integer column vertical calculation]
    Question type: Integer multiplication
    Original question: 21×20
    Solution:
    21×20 = 420
    Column vertical calculation:

							2	1
✖							2	0
							0	0
						4	2
						4	2	0

[6/7 Integer column vertical calculation]
    Question type: Integer multiplication
    Original question: 41×20
    Solution:
    41×20 = 820
    Column vertical calculation:

							4	1
✖							2	0
							0	0
						8	2
						8	2	0

[7/7 Integer column vertical calculation]
    Question type: Integer multiplication
    Original question: 40×40
    Solution:
    40×40 = 1600
    Column vertical calculation:

							4	0
✖							4	0
							0	0
					1	6	0
					1	6	0	0

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>>注：本次最多计算 7 道题。

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