Given that a family has three children, and one of them is a girl, what is the probability of having at least one boy? List analysis method The total number of male and female distribution list of 3 children is the third power of 2, which is 8. Why do we consider 8 kinds of children? Why are there differences between male and female! The answer is 6 / 7, which is the birth probability of several children. One of them is female, so there is no male list 1 male and female 2 women and men 3 men and women 4 women and men 5 women 6 men and women 7 women and men Because one of them was a girl and came to seven conclusions, and six of them were boys So it's 6 / 7 Why do you think about eight, men and women and men and women

You don't make clear the difference between the arrangement and combination of the core problem. The core problem is that there is a difference between the three children. The eldest child is a woman and the second child is a woman. These are two things. (1) the probability of having three girls is 1 / 8, not 1 / 4 (0,1,2,3 girls), or from the probability point of view, it is an event of unequal probability

A family has three children, (1) the probability of having two boys and one girl in the family, (2) the probability of having at least one boy in the family

Use B and G to represent boys and girls respectively, and use "tree" to list all the results: the probability of the family having two boys and one girl is 38, and the probability of the family having at least one boy is 78

If there are two children in a family and one of them is known to be a girl, then the probability that the other is a girl is ()
A. 14B. 13C. 34D. 12

What is the formula for the relationship between A1 and D in the arithmetic sequence?

a(n)=a(1)+(n-1)×d
There is no relationship between A1 and D~

Group words with deliberation

The best scheme is selected through repeated consideration

How to find the general term formula after solving A1 and D with arithmetic sequence

The difference between one kind of atom, the same kind of atom, the same kind of atom, and different kinds of atoms? Do elements have to be made up of atoms?

The same kind of atoms must be atoms, and the number of protons, neutrons and electrons are all the same, otherwise they are different kinds of atoms

All formulas of arithmetic sequence

The following n are all integers: arithmetic sequence formula: an = a1 + (n-1) d [basic formula] the first N-term sum formula is: SN = Na1 + n (n-1) d / 2 [sum] Sn = n (a1 + an) / 2 Tolerance d = (an-a1) / (n-1) [generalization] if n, m, P and Q are positive integers, if M + n = P + Q, then there is am + an = AP + AQ, if M + n = 2p, then am +

An element is a general term for a class of elements. Different atoms of the same element must be the same, while atoms and ions of the same element are different

Element is the general term of the same kind of atoms with the same number of protons (nuclear charge)
The number of protons and electrons must be the same for different atoms of the same element
The number of extranuclear electrons of atoms and ions of the same element is different

Arithmetic sequence and formula

The formula of arithmetic sequence is to divide the number of multiplication terms by two