At present, primary school papers not only test students' mastery of basic knowledge, but also test students' thinking ability, hands-on ability and computing ability. Especially in math test papers, there are questions similar to "intelligence questions" to stimulate students' brains and develop their divergent thinking ability.
There was a math final exam in the second grade of primary school. Of the 58 students in the class, only 2 made correct answers. It is too difficult for parents to make a sound after reading it, and 985 Xueba will make mistakes. Hua Xiaomei will show you this "weird" math final exam. How difficult is it? Why do many pupils do something wrong? Parents say they won't do it, even 985 Xueba will make mistakes.
The topic of the final exam of mathematics in the second grade of primary school is very concise, but it is a question that primary school students are prone to make mistakes. "It took 9 seconds for the clock to strike 4, and how many seconds did it take to strike 8?" Many primary school students feel very simple after reading this question. They directly give the answer 9*2= 18 seconds, and can write the answer 18 seconds, which are all wrong answers. Parents are also puzzled after reading it. They ask, "It takes 9 seconds for a clock to strike four times, isn't it twice as long as 9 seconds to strike eight times?" 18 second should be right. "Even 985 Xueba has racked its brains for this problem. I can't figure out why it takes 9 seconds for the clock to strike four, but it doesn't take 18 seconds for the clock to strike eight. " In fact, this question mainly examines students' thinking ability. Don't underestimate that the topic is simple, but easy to make mistakes.
The biggest misunderstanding of this question is that "the clock strikes four times and takes nine seconds". We should take it for granted that "when the clock strikes eight, it is 18 seconds". If we think so, we are all wet. So this problem is very similar to "intelligence problem", which can expand students' thinking ability and practical ability and develop students' intelligence.
The key to solve this problem is that "the clock strikes four times and takes nine seconds". We should not think about how many seconds we knock, but should calculate this problem according to the law of the clock ringing in our life. As we all know, when the clock strikes the second time, there will be a blank interval between the first time and the second time, so when the clock strikes four times, there will be three blank intervals between 1, 2, 3 and 4. A blank interval is 3 seconds, and there will be 7 blank intervals when the clock strikes 8, so the correct answer of "It takes 9 seconds for the clock to strike 4, and how many seconds is it when it strikes 8" is 3*7=2 1 second; The correct answer is 2 1 sec. Have you thought of the clever one?