Question

три школьника решали задачи. первый ошибся в 15 задачах, второй- в 12, а третий - в 7. оказалось, что один школьник решил в три раза больше задач, чем решил другой. сколько задач решил третий?

Answer 1

Ответ:12

Пошаговое объяснение:

3(x-15)=(х-7)

2х=38

Х=19

Третий ученик решил правильно

19-7=12

Answer 2

Problem Analysis

Three schoolchildren were solving math problems. The first child made 15 mistakes, the second child made 12 mistakes, and the third child made 7 mistakes. It is known that one of the children solved three times as many problems as the other. We need to determine how many problems the third child solved.

Solution

Let's assume that the first child solved x problems and the second child solved y problems. According to the given information, one child solved three times as many problems as the other. We can set up the following equation:

x = 3y We also know that the first child made 15 mistakes, the second child made 12 mistakes, and the third child made 7 mistakes. The total number of mistakes made by the three children is:

15 + 12 + 7 = 34

Since each mistake corresponds to one problem, we can set up another equation:

x + y + 7 = 34 Now we can solve these two equations to find the values of x and y.

Solving the Equations

Substituting the value of x from the first equation into the second equation, we get:

3y + y + 7 = 34

Simplifying the equation, we have:

4y + 7 = 34

Subtracting 7 from both sides, we get:

4y = 27

Dividing both sides by 4, we find:

y = 6.75

Since we cannot have a fraction of a problem, we can round this value to the nearest whole number. Therefore, the second child solved 7 problems.

Substituting this value back into the first equation, we find:

x = 3 * 7 = 21

Therefore, the first child solved 21 problems.

Finally, to find the number of problems solved by the third child, we add the number of problems solved by the first and second children and subtract it from the total number of problems:

Total problems - (problems solved by the first child + problems solved by the second child) = problems solved by the third child

34 - (21 + 7) = 6

Therefore, the third child solved 6 problems.

Answer

The third child solved 6 problems.