Use the numbers 0,1,2,3,4,5 to form a number without repetition 1: How many 6 digits can be made up 2: How many natural numbers larger than 300000 can be formed 3: How many four digits can be made up that are multiples of 25 We need to calculate the process

1. If 6 digits are formed, 6 digits can only be 1,2,3,4,5
5 bits can only be 6-1 = 5 cases
Four four
.
There are 5 * 5 * 4 * 3 * 2 * 1 = 600 6 digits
2. If it is larger than 300000, the sixth bit can only be 3,4,5, and the other bits are the same
There are 3 * 5 * 4 * 3 * 2 * 1 = 360
3. If it is a multiple of 25, then the last 2 bits should be 50, such as xx50
Then 6 bits can only be used in 1,2,3,4 cases
There can only be three cases
4 2
3 1
So there are only 4 * 3 * 2 * 1 = 4 kinds of 6 digits

Using 0,1,2,3,4,5, what is the number of numbers greater than 201345 and without repetition?
There should be a process

Because this number is the smallest of all the numbers starting with 2, there are (a 55-1) numbers starting with 2, and each a 55 starting with 3.4.5! Because the numbers starting with 3.4.5. Are larger than those starting with 2! So there are (4 * a 55-1) = 479

2.5 times of a number, 3.6 less than 4 times of it

3.6÷（4-2.5）
=3.6÷1.5
=2.4
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What is the number? 3 / 5 of a number minus 30, the difference is exactly 2 / 2 of 90
1. What's the number that is 6 / 6 less than 5 / 5
If you subtract 30 from three fifths of a number, the difference is exactly one-half of 90

Let X be the number
1/6x+2=1/5x
x=60
Let a number be y
3/5y-30=90÷2
y=125
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Use the numbers 0,1,2,3,4,5 to form a number without repetition 1: How many 6 digits can be made up 2: How many natural numbers larger than 300000 can be formed 3: How many four digits can be made up that are multiples of 25 We need to calculate the process