题目

一块钢板的形状如图所示，已知AB＝12cm，BC＝13cm，CD＝4cm，AD＝3cm，∠ADC＝90°，则这块钢板的面积是 ______cm2． 答案：【答案】24【解析】连接AC．利用勾股定理可求出AC的长，根据△ABC的三边关系可得△ABC是直角三角形，根据三角形的面积公式可求出△ABC与△ACD的面积，进而求出四边形ABCD的面积．连接AC，由勾股定理得：AC5．∵AB=12，BC=13，AC2+AB2=BC2，即52+122=132，故△ABC是直角三角形，∠CAB=90°，故四边形ABCD的面积=S△AOnce a group of 17-year-old schoolboys decided to break the world basketball marathon record(马拉松记录). They wanted to play for ninety hours and that is to add six hours to the record. Each team had nine players, with five at a time. The boys decided each person would play 21. 5 hours and then rest for 2 hours. Then they started at 6 o’clock in the evening. The first night was very hard for the players. When it was their turn to rest, they were too excited(兴奋的) to fall asleep at once. After sleeping for a short time, they had to play again. On the second night, they fell asleep as soon as they stopped. Some of them had trouble with their feet and hands, but the only serious problem was a psychological(心理上的) one. Each boy was thinking：why am I doing this？How can I play any longer？After the third night, the players knew they could finish the ninety hours. The basketball on the fourth night was very slow. But in the final hours, the players got better. For the last few minutes, the players looked as fresh as when they started. How happy everyone was！小题1:In the story, there were _______ schoolboys playing basketball marathon. A．9B．14C．17D．18小题2: Before this basketball marathon, the world record was _______.A．84 hours B．86 hours C．90 hours D．96 hours小题3:The first night was hard for the players to fall asleep because _______.A．they were too excitedB．they only slept for a short timeC．no one watched them playD．it was very long小题4:“…the players looked as fresh as when they started” here “fresh” means _____.A．新鲜的B．兴奋不已的C．精神饱满的D．伤痕累累的小题5: Which of the following sentences is wrong？_______.A．Some of the boys were hurt when they played.B．It was hard for the players to fall asleep at night.C．The boys started playing at 6 o’clock in the evening.D．In the end, all the boys felt happy.