The boys shouted and laughed as they ran about in playground. It was near the end of term in a school in Germany about two hundred years ago. Soon school would be over for a few weeks. No wonder （难怪） they felt happy！
Their teacher watched them from the classroom window. He did not feel happy at all. End of term for him meant a lot of work. He thought hard. what could he find for the boys to do that would keep them quiet for a long time？ Then he could deal with （处理） his own work.
All of a sudden he had an idea. when the bell rang for the end of playtime, he was smiling.
One by one the boys came back to the classroom and sat at their desks.
Listen, boys, said the teacher. I want you to take your pencils and write down all the numbers from 1 to 100. When you have done that, add them all up. And no talking,mind（记住了）！”
The teacher smiled as the boys began their work."That should keep them busy for a bit, "he said to himself. But he was wrong Five minutes later the slowest boy was still writing down the date. Most of the other boys had just begun to add the numbers. One boy, however, put his pencil down.
“ What's the matter,Karl？” asked his teacher.“ Can't you do it？”
“Yes,sir，” replied the boy，“ But i have finished. The answer is 5,050.”
Nobody in the room believed him. How could a boy of ten add up all those numbers in such a short time？
Perhaps you had better tell us how you got your answer, 'the teacher told him.
It was easy, said the boy. First of all I added up 1 and 99， and that made 100. Then I kept on adding 3 and 97， 4 and 96， and so on until I got to 49 and 51. Each time the answer was 100， and so I had 49
hundreds in all. That made 4， 900. Then I added on the two numbers I left out, 50 and 100. and i got the answer 5,050.
The teacher groaned. It seemed as if the boy was quite right Now. he would have to find something else for them all to do.
Today we have forgotten the name of the teacher, but not the little boy who was so quick at his sums. His name was Karl Gauss.
Karl Gauss became a famous scientist. One of his great interests was astronomy（天文学）， the study of the stars. Before he died in1855，he had written 155 books.