Question

Ученик купил по олинаковой 9 тетрадей в линейку и 5 в клетку. За тетради в линейку он заплатил на 12 рублей больше. Сколько стоили тетради в линейку? Сколько стоили тетради в клетку?

Answer 1

9-5= 4 на четыри штуки  тетрадей в линию больше чем в клетку.
12 :4 = 3 рублей стоит одна тетрадь в линию, но по условию цена в клетку такая  же.
3* 9 =27 рублей стоят тетради в линию
3*5= 15 рублей стоят тетради в клетку

Answer 2

В линейку - 27 рублей, В клетку - 15 рублей

Answer 3

Problem Analysis

The student bought 9 notebooks with lined paper and 5 notebooks with grid paper. The total cost of the lined notebooks was 12 rubles more than the total cost of the grid notebooks. We need to find the individual prices of the lined and grid notebooks.

Solution

Let's assume the price of a lined notebook is x rubles and the price of a grid notebook is y rubles.

The total cost of the lined notebooks is 9x rubles, and the total cost of the grid notebooks is 5y rubles.

According to the problem, the total cost of the lined notebooks is 12 rubles more than the total cost of the grid notebooks. So we can write the equation:

9x = 5y + 12

To find the values of x and y, we need another equation. Let's use the information that the student bought a total of 14 notebooks:

9 + 5 = 14

Now we have a system of two equations:

9x = 5y + 12 9 + 5 = 14

We can solve this system of equations to find the values of x and y.

Solving the System of Equations

Let's solve the system of equations using the substitution method.

From the second equation, we can express 9 as 14 - 5:

14 - 5 = 14

Substituting this value into the first equation:

(14 - 5)x = 5y + 12

Simplifying:

9x = 5y + 12

Now we have a single equation with one variable. Let's solve for x:

9x - 5y = 12

To isolate x, we can add 5y to both sides:

9x = 5y + 12

Dividing both sides by 9:

x = (5y + 12) / 9

Now we have the value of x in terms of y. We can substitute this expression into the equation 9 + 5 = 14 to solve for y.

9 + 5 = 14

Simplifying:

14 = 14

This equation is true for any value of y. Therefore, there are infinitely many solutions for y.

Conclusion

In conclusion, the price of the lined notebooks, x, can be expressed as (5y + 12) / 9, where y can take any value. The price of the grid notebooks, y, can take any value.