Two beads can be used to represent several four digits on the counter, and they are arranged in the order from small to large

1001；1010；1100；2000
There are four four digits in total
A counter is like an abacus

Seven beads are used to indicate three digits on the counter. The sum of the largest and the smallest is () a.707: b.8
6:C.860

The largest number is 700, and the smallest number is 7
The sum is 700 + 7 = 707
A

I dial five beads on the counter to indicate a number. Can you guess what number I may dial?

There are five cards in red, yellow and green, each with the letter ABCDE. Now we take five cards out of them. There are several ways to choose different letters and complete colors
The answer is [c53c21c11) / A22] * A33 and [c51c41c22) / A22] * A33. I don't understand why I divide by A22 and multiply by A33,

Take [c53c21c11) / A22] * A33 for example, it may take 3 red, 1 Lu, 1 yellow, it may also be 1 red, 3 green, 1 yellow may also be 1 red, 1 green, 3 yellow, just like sorting 1, 1, 3 numbers in red, yellow, and green positions, so multiply by A33, but because it has two numbers that are the same, divide by A22, for example, 123

There are five red, yellow and blue cards each, and the five cards of the same color are marked with ABCDE five letters. Now take any four of these 15 cards, how many kinds of methods are required to have different letters and complete three colors? I have calculated that there are 5x4x3x6 = 360 kinds. Why is the answer 180 kinds? What do I calculate more

There must be a kind of color card will choose two, these two originally have no order, you calculate like this is equivalent to two times. For example, red a yellow B blue C Red D and red D yellow B blue C Red a

There are 5 red, 5 yellow and 5 blue cards respectively. The 5 cards of the same color are marked with ABCDE. Now, 4 of them are taken from 15 cards, and the letters are required to be different from each other

The title is incomplete, please add

It is known that there are five cards in red, yellow and green, and they have ABCDE respectively. Now take five of them. How many kinds of cards are required to have different letters and complete three colors

Letter ABCDE five cards
It's dead
So in fact, different ways are just different in the color arrangement of each card
There are two cases of different colors: three of them have the same color, or two of them have the same color
So the method is (10) * 3 * 2 * 1 + (10) * (3) * 3 * 2 * 1 = 180

Write the 11 letters "probability" on the 11 cards respectively, and select 7 of them randomly, and calculate the probability that the result of arrangement is ability

You can think of simple point, one by one to extract
The probabilities of taking data from the left are multiplied in turn, that is, P (a) * P (b) * P =1/11*2/10*2/9*1/8*1/7*1/6*1/5=?

There are three cards marked with letter A and six cards marked with numbers 1, 2, 3, 4, 5 and 6 respectively. If any six cards are selected to form a brand, the number of different brands can be formed

A6*C65+C64*A6/2+C63*A6/6+A6
=6*5*4*3*2*1*6+15*6*5*4*3+20*6*5*4*3*2*/6+720
=4320+5400+2400+720
= 12840

There are three cards marked with the letter A and six cards marked with 1, 2, 3, 4, 5 and 6 respectively. If you take any five of them, what is the total number of different brands?
The answer seems to be 4020

10020, a don't sort, numbers sort

Two beads can be used to represent several four digits on the counter, and they are arranged in the order from small to large