"My Hogwarts has a big problem new ( Find the latest chapter!

After being haunted last semester, Ravenclaw College has had another big problem recently.

This morning, a famous fourth-grade little wizard hurriedly came out of the lounge. He only found out after breakfast in the auditorium. He was waiting for the book for the first potion class.

Professor Snape is not a kind professor. Don’t say he will forgive you for forgetting to bring your books. This little wizard has been at Hogwarts for four years and has never seen Snape treat that student. Laughed, except for sneers and sneers.

He could only hurried back to the lounge, praying in his heart that the riddle of the door knocker had not been changed, or that he had something urgent to give him a simpler one.

But when he returned to the door of Ravenclaw's lounge, he was dumbfounded when he heard today's question.

"Use the ten numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 to form a five-digit number. What is the total number of five-digit numbers containing three odd numbers and two even numbers? Piece?"

"Here..."

The fourth-grade little wizard stammered at the knocker on the door that seemed to be convulsive, and immediately wondered if he had heard it wrong.

"Um... please put the question aside."

Knocker Eagle looked very impatient and repeated the question again, as if the little wizard had interrupted what it was doing.

"What's the problem? Five digits? And what are the odd and even numbers?" The little wizard collapsed, "All right, Brother Eagle, I will be late if I don't take out the book, Professor Snape will call me Skin cramps are made into potion materials!"

However, the Knocker Eagle simply ignored his request. In the past, the little wizard encountered an emergency but could not answer its questions, but the door knocker that enforced the law impartially never let them go privately.

The little wizard had no choice but to look at the time, he could only grit his teeth and ran towards the classroom.

He would be scolded if he didn't get a book, but if he was late and didn't get a book, he could hold a death banquet today next year.

After the little wizard who got in the way was fooled away, the Knocker Eagle was finally able to continue to count.

But before long, a new group of little wizards returned from the auditorium.

They are Ravenclaw third-grade students. Because there is no class this morning, they can go back to the dormitory to spend a leisurely half day after breakfast from the auditorium.

"Have you finished the homework assigned by Professor Lockhart?" A third-grade girl smiled and talked to the boy with white-haired facial paralysis next to her.

"finished."

The little witch exclaimed: "So fast, the defense against the Dark Arts class has a lot of homework, and the professor stipulates that at least 15 inches of parchment should be written. How much did you write?"

"18 inches."

The boy's attitude seemed rather cold, but the little wizards and little witches around him were not surprised. They had been classmates together for three years, and of course they knew that Ian Campbell was like this to everyone.

Although Ian was very indifferent, the little witch was still very enthusiastic, whispering.

"You always finish your homework first. Who did you do it with? Yesterday, Monica and I wanted to go to do your homework with you, but we didn't see you in the lounge."

Ian's coldness is coldness, but he answers every question.

"Lynn of Slytherin and Cedric of Hufflepuff."

"I heard that you and them are friends, and it is said that both of them are top students in their respective colleges, and Lynn Belloc has been the number one in our level since the first grade."

When Ian heard what she said, he couldn't help but remember that "Lynn"'s recent performance was completely unworthy of his Slytherin's best student and the title of No. 1 in the third grade.

While they were chatting, a group of people had already arrived in front of the Slytherin common room. The knocker hawk who was counting saw that they could only stop, and asked Lynn's questions impatiently. .

"Use the ten numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 to form a five-digit number. What is the total number of five-digit numbers containing three odd numbers and two even numbers? Piece?"

Ravenclaw's Little Wizard: ∑(￣□￣;)

"This... what riddle is this?"

"Why make these numbers into five digits?"

"What is an odd number? What is an even number?"

A group of little wizards suddenly became Muggles. They have pure-blood, mixed-blood and Muggle family backgrounds. Basically, pure-blood and mixed-blood little wizards have never attended a Muggle elementary school, while those from a Muggle family have gone to elementary school. Not yet to the level of learning this kind of knowledge.

Ian also heard this question. He was born noble. Although he never went to elementary school, he had a special tutor at home to teach him when he was young, so at least he knew what odd and even numbers were.

Looking at the little wizards around him who had no heads, he could only explain to them.

"An even number is a number that is divisible by 2. An odd number has a formula. Any number derived from 2n+1 is an odd number."

These little wizards still understand the most basic mathematical knowledge. After all, they are all Ravenclaw students, and they immediately understood Ian's meaning.

"That is to say 1, 3, 5, 7, 9 are odd numbers, and 2, 4, 6, 8 are even numbers."

"There is such a distinction between numbers." The little wizard with a pure-blood family was very surprised.

The Muggle-born little wizard explained to him: "This is the classification and summary of Muggle mathematicians. The question asked by the knocker should also be a question about Muggle mathematics."

"So what about 0? Is 0 odd or even?" Every little wizard in Ravenclaw has the pursuit of knowledge, and soon the little wizards are attracted by the knowledge of mathematics.

Without Ian's answer, a clever little wizard deduced it.

"0 should be considered an even number~lightnovelpub.net~ because there is no number that can satisfy 2n+1=0, and 0÷2=0 is an even division, so 0 should be an even number."

There is actually a loophole in what he said. The negative one-half can be brought into the formula to get 0, but Ian did not remind them that it is not easy for them to understand odd and even numbers in a short period of time, what about negative numbers. It's better to talk about it later, the province is confused.

"Five digits. How many of them contain three odd numbers and two even numbers? This range is too big. If you count one by one, you can count it for three days."

"The door knocker won't give us unsolvable problems." Xiaoying shared calmly, "There must be a simple way to calculate this number in a short time!"

They didn't have classes in the morning, so they gathered in front of the door and began to think about an easy way to solve this problem.

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