论文部分内容阅读
[题目一]小明所在班级的人数不足40人,但比30人多。那么这个班男、女生人数的比不可能是()。A.2:3 B.3:4 C.4:5 D.3:7(第十九届华罗庚金杯少年数学邀请赛初赛试卷·小学高年级组第4题)我是用估算、排除的方法解的。由题意可知,小明所在班级的人数在31~39之间。如果把全班人数平均分成2+3=5(份),则每份人数为7人,总人数为7×5=35(人);如果把全班人数平均分成3+4=7(份),则每份人数
[A] Xiaoming class where the number of less than 40 people, but more than 30 people. Then the class male, the ratio of the number of girls can not be (). A.2: 3 B.3: 4 C.4: 5 D.3: 7 (The 19th Hualanggen Gold Cup Junior Math Invitational Contest Test Paper, Grade 4 of the Senior High School) I used the method of estimation and exclusion of. By the title we can see that the number of classes where Xiao Ming is between 31 to 39. If you divide the class equally into 2 + 3 = 5 (copies), each will be 7 in total, with a total of 7 × 5 = 35 (people). If you divide the class equally into 3 + 4 = 7 ), Then the number of each