There are three cards with 1 and 2, 4 and 6, 7 and 8, 6 can be used as 9. How many different three digit numbers are there Why is the correct answer 72

96. The combinations are: (1,4,7) (1,4,8) (1,6,7) (1,6,8) (2,4,7) (2,4,8) (2,6,7) (2,6,8) (1,9,7) (2,9,7) (1,9,8) (2,9,8)
Each combination has 6 different permutations, with a total of 12 * 6 = 96 different three digit numbers

There are five cards with 0 and 1, 2 and 3, 4 and 5, 6 and 7, 8 and 9 on the front and back sides respectively. How many different three digits can be formed by putting any three of them together? How many even numbers are there? Since my calculation is different from the answer, please give the disassembly steps. 3Q!

(1) Let's look at the highest position first. There are nine choices,
In other positions, two cards can be arranged first, and then each card has two different choices
There are 9 * a (4,2) * 2 * 2 = 9 * 12 * 4 = 432
(2) Classification
1. The last position is 0. Two cards are arranged in other positions, and each card has two different choices,
A (4,2) * 2 * 2 = 48
2. The last place is 2,4,6,8
There are four choices for the last, seven choices for the first and six choices for the tenth
There are 4 * 7 * 6 = 168 species,
Therefore, there are 48 + 168 = 216 even numbers

There are four cards, each with a number on the front and back. The first card contains 0 and 1, the second 2 and 3, the third chapter contains 5 and 6, and the fourth chapter contains 7 and 8
How many different double digits can be made up of two cards in a row

I counted 67
The first is C4 (2) x A4 (2) - 5 = 67
First, take two cards, then choose two numbers from the four numbers of the two cards, and subtract the five numbers with ten zeros 01 02 03 05 06

The front and back of the four cards are respectively written with 0 and 1, 2 and 3, 4 and 5, 6 and 7. How many different three digit numbers can be formed by putting the three cards together?

It can be divided into three steps: the first step: 8-1 = 7 numbers can be put in 100 bits; the second step: 6 numbers can be put in 10 bits; the third step: 4 numbers can be put in one bit. According to the principle of step-by-step counting, 7 × 6 × 4 = 168 numbers can be formed

Where is the ox man? Why is the water in heaven and the earth 60%. How does the order of water, fire, wood, gold and earth come from

There are many orders of five elements. You are one of them. For example, ten numbers and five elements come from the heavenly stems. A and B (numbers 1 and 2) are wood, wood makes fire, C and D (numbers 3 and 4) are fire, fire makes earth, Wuji (numbers 5 and 6) is earth, earth makes gold, Gengxin (numbers 7 and 8) is gold, gold

How to represent the five elements of gold, wood, water, fire and earth?
Which numbers are gold
Which ones are wood

Five elements and numbers
1. 2 is wood, 1 is Yang wood, 2 is Yin wood
3. 4 is fire, 3 is Yang fire, 4 is Yin fire
5. 6 is soil, 5 is Yang soil, 6 is Yin soil
7. 8 is gold, 7 is Yang gold, 8 is Yin gold
9. 10 is water, 9 is Yang water and 10 is Yin water
Orientation and characteristics of the five elements
A and B Yinmao Oriental wood; Bing Dingji Southern fire; Wuji central soil; Chenxu chouwei Siku soil; Geng xinshenyou western gold; Ren guihaizi northern water
"Wood" has the characteristics of growth and straightness. Wood is the master of benevolence;
"Fire" has the characteristics of fever and upward, fire is the main ritual, its impatience, its passion;
"Earth" has the characteristics of breeding and breeding. It is believed by the owner of the earth, with heavy nature and deep feeling;
"Jin" has the characteristics of quietness and restraint;
"Water" is cool and downward. It is intelligent, intelligent and kind
The order of five elements is: water makes wood, wood makes fire, fire makes earth, earth makes gold, and gold makes water
The order of the five elements is: water conquers fire, fire conquers gold, gold conquers wood, wood conquers earth, and earth conquers water

In the second volume of the fifth grade of the people's education press, the questions were divided first, and then the sizes of 7 / 12 and 5 / 16, 10 / 27 boxes, 7 / 18, 8 / 3 and 11 / 4 and 16 / 9 were compared

Divide the following groups into 5 / 8 and 7 / 24 3 / 5 and 5 / 14 5 / 24 and 3 / 4 4 / 5 and 5 / 6

After 5 / 8 and 7 / 24, they are 15 / 24 and 7 / 24
After 3 / 5 and 5 / 14, they are 42 / 70 and 25 / 70
5 / 24 and 3 / 4 are 5 / 24 and 18 / 24
After 4 / 5 and 5 / 6, they are 24 / 30 and 25 / 30

3 / 8 and 6 / 5

15/40 48/40

How to divide 5 out of 8 and 4 out of 7
How to divide 1 / 4 and 5 / 16

1. The problem of 5 / 8 and 4 / 7 is to find the least common multiple of denominator "8" and "7". 8 and 7 are coprime numbers, and their least common multiple is 7 × 8 = 56,5 / 8 = (5 × 7) / (8 × 7) = 35 / 56 Both numerator and denominator

There are three cards with 1 and 2, 4 and 6, 7 and 8, 6 can be used as 9. How many different three digit numbers are there Why is the correct answer 72