In addition to strengthening routine calculation training, it is also very important to exercise problem-solving thinking in primary school mathematics. Starting today, Ai Xuewa will launch a series of articles on mathematical thinking training in primary schools to train children in various problem-solving thinking.

The topic of the first issue is to unlock the password lock. Let's look at the topic first.

Dad bought Xiaoming a password lock to lock his little secret. However, in order to test Xiao Ming, my father confused the three digits of the password lock and only gave the following five tips. Can you help Xiao Ming deduce the correct password and unlock it?

Hint 1:

One of the numbers 682 is correct, and the position of this number is correct.

Tip 2:

One number in 6 14 is correct, but the position of this number is incorrect.

Tip 3:

In the number 206, there are two correct numbers, but neither of them is in the right position.

Tip 4:

None of these figures is correct.

Tip 5:

One of the 870 numbers is correct, but the position of this number is incorrect.

Think for yourself, students. Can you infer the correct unlock password from the above five tips?

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This is not a very gorgeous dividing line.

The following is the process and answer of the question.

The first step to solve the problem:

Starting with 1 and the second prompt, assuming that the number 6 is correct, the position in 1 and the second prompt is contradictory, so the number 6 can be excluded.

The second step to solve the problem:

According to the fourth hint, the numbers 3, 7 and 8 are incorrect and can be excluded.

Combined with 1 prompt, the third digit after excluding the number 8 is 2.

The third step to solve the problem:

The third digit is 2. Combined with the third hint, one digit is 0, but the position is wrong, so it is not in the second place, nor can it be the third (the third digit is 2), so it is concluded that the first digit is 0.

The fourth step to solve the problem:

Now we are missing the second number. Combined with the second prompt, the remaining second number is 1 or 4. Suppose the number 1 is correct, which contradicts the "incorrect position" in the condition, so the second digit is 4.

Recommended mathematical calculation training questions

40 sets of special training of three-digit multiplied by two-digit in primary school mathematics (printed version)

40 sets of intensive training for math calculation problems in the third grade of primary school (printed version)

40 sets of intensive training for math calculation problems in the second grade of primary school (printed version)