Find a fairy tale about mathematics

Odd and even numbers

Zheng Chenxi, the first primary school in Lingyang Town, Cili County, Hunan Province

In the activity class, Mr. Black Bear smiled and said to everyone, "Shall we play a game?"

"good!" The little animals answered in unison. "Please prepare two small notes for each of you." Teacher Black Bear cleared his throat and said. These little animals don't know what game Mr. Black Bear wants them to play. One by one, their excited eyes lit up, and soon all the little notes were ready.

Teacher Black Bear looked around the class and said, "Please write an odd number and an even number on two small pieces of paper, and then take one in each hand. Don't show it to me or your classmates. "

Small animals just learned odd and even numbers not long ago, and in a short time, everyone met the requirements put forward by Mr. Black Bear. "Listen," Mr. Black Bear said clearly, word by word, "please multiply the number in your right hand by 2, the number in your left hand by 3, and then add up the products. Don't work out the sound. "

When all the animals were counted, Mr. Black Bear asked the odd animals to line up. If the number of people is even, line up. The little animals stood still, looking at Mr. Black Bear with interest, guessing what he wanted them to do next.

"All right!" Teacher Black Bear pointed to the odd-numbered row of small animals and said, "You have an odd number in your left hand."

It pointed to another row of small animals and said, "You have an even number in your left hand."

Two rows of small animals spread their palms, but yes, Mr. Black Bear is absolutely right.

Small animals were so surprised that they couldn't help asking, "Teacher, how do you know?"

The black bear teacher then analyzed: "

Odd number × 2 = even number × 3 = odd number

Even number × 2 = even number × 3 = even number

Even+even = even+odd = odd.

When the left hand is odd, odd ×3 is odd, odd+even (right hand is even ×2), and the result is odd. And if the right hand is odd, odd ×2 becomes even, even+even (the left hand is even ×3), and the result is even.

This is the reason why the final result is the same as the odd-even number of the left hand, and it is also the basis of my guess. "

The little animals suddenly realized ...

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