Tomorrow s math competition??? After the math competition

Believing in yourself is the best.

You have to have faith to do well.

If Xiao Ming answers question x correctly, he answers (20-x) 2 questions incorrectly, and he does not answer (20-x) 2 questions.

5x+(20-x)/2*0+(20-x)/2*(-1)=675x-(20-x)/2=67

10x-(20-x)=134

10x-20+x=134

11x=154

x=14Answer: Xiao Ming answered 14 questions correctly.

If the teacher guessed correctly that Si Si De Jin then Da Ming was also right that he didn't get gold, contradictory!

If the teacher guessed correctly that Da Ming didn't get gold, plus the above guess Si Si Dejin was wrong, that is, Qiuqiu got gold, then the teacher said that Qiuqiu didn't get gold, it was right, and it was a contradiction!

If the teacher guessed correctly that Qiuqiu didn't get copper, it was right, then Daming didn't get gold, it was wrong, so it was Daming who got gold, and Qiuqiu got silver.

To sum up, the Ming Dynasty gets gold, the autumn gets silver, and the Si Si gets copper.

Stellkin = Event A

Da Ming didn't get money = event B

Autumn and Autumn Didn't Get Copper = Event C

Event where the teacher guessed correctly = x

There is only one =x in abc

1: If a=x, then b=x, the teacher guessed more than one thing, not right.

Two: If b=x, then Sisi and Daming did not get gold, Qiuqiu only got gold, not copper, c=x, no.

Three: If c=x, then Ming gets gold, autumn gets silver, Sisi gets copper, and the teacher only guesses 1 correctly to be established.

So only the third case is correct.

Daming gets gold, Sisi gets copper, and autumn is silver.

If Sisi gets gold is true, then Daming doesn't get gold and it's true, so the first sentence guesses wrong If Daming doesn't get gold is true, then Qiuqiu doesn't get copper should be false, that is, Qiuqiu gets copper, then Daming gets silver, Sisi can only get gold, so it becomes a two-sentence guess that is correct, and the question does not match.

If there is no copper in autumn and autumn, it may be gold in the Ming Dynasty, copper in Sisi, and silver in autumn and autumn. In line with the topic.

Si Si got copper, Daming got gold, and autumn got silver.

Set the answer to the correct x.

5x+(-3(20-x)=60

x=15Answer: Xiao Ming answered 15 questions correctly.

Suppose you answer x correctly, because there are as many correct answers as there are incorrect answers, so the wrong answer is also x, then 5x-3x=61

i.e. x = the answer is not true.

Reason 1 must be a natural number, reason 2 2x must be less than or equal to 20 questions are not valid!!

The phrase "as many as those who answer incorrectly" is removed from the phrase below.

Let x, wrong y, 5x-3y=61, x+y 20, and x, y are natural numbers or 0 side x=(61+3y) 5, to ensure that x is a natural number, 61+3y is a multiple of 5, and the natural number y less than 20 that meets the conditions is only , respectively, can meet x+y 20 only y=3, x=14

That is, 14 questions were answered correctly, 3 questions were answered incorrectly, and 3 questions were not answered.