What are the wide angles of mathematics from the second volume of the first grade to the second volume of the sixth grade of PEP? Write clearly!

What are the wide angles of mathematics from the second volume of the first grade to the second volume of the sixth grade of PEP? Write clearly!


There is no second grade volume 1: simple arrangement and combination, such as which two digits 1 and 2 can be arranged into; simple reasoning, such as who has what kind of goods in hand. Second grade volume 2: there is no third grade volume 1: collocation, competition times. Third grade volume 2: simple set and equal substitution



1. There are 10 table tennis balls of red, yellow, white and three colors in one bag. At least how many table tennis balls must be taken out to ensure that all the three colors can be taken? Why? (and write the formula)
2. There are 40 pieces of the same wood in a cloth bag, 10 of which are numbered 1, 2, 3 and 4. Q: how many pieces of wood must be taken out at least at one time to ensure that there are at least three pieces of wood with the same number? Why? (and write the formula)
Qsmm: there seems to be something wrong with the second question you answered. Why take it three times? The topic is that you can only take one time, at least how many pieces of wood you need to take before


1. There are 10 table tennis balls of red, yellow, white and three colors in one bag. At least how many table tennis balls must be taken out to ensure that all the three colors can be taken? Why? (and write the formula)
In the worst case,
Take out 10, all in the same color
Another 10 are all the same color
At this time, just take out one is the third color
The formula is: 10 × (3-1) + 1 = 21
2. There are 40 pieces of the same wood in a cloth bag, 10 of which are numbered 1, 2, 3 and 4. Q: how many pieces of wood must be taken out at least at one time to ensure that there are at least three pieces of wood with the same number? Why? (and write the formula)
Four of them were taken out for the first time, 1, 2, 3 and 4 respectively
In the second time, four were taken out, which were 1, 2, 3 and 4 respectively
At this time, as long as one is taken out, there will be three identical numbers
The formula is: 4 × (3-1) + 1 = 9