Question

Карандаш и ручка стоит вместе 8 рублей, а 5 карандашей и 2 ручки стоят 25 рублей.Сколько стоит карандаш и сколько стоит ручка? Помогите пожалуйста целый день голову ломаем)

Answer 1

Пускай карандаш стоит х руб, а руччка у.

сост.систетему:

х+у=8

5х+2у=25 

 

х+у=8  І-2 

5х+2у=25

 

 

-2х-2у=-16

5х+2у=25 

 3х=9

х=3

3+у=8

у=5

то есть,  Карандаш стоит 3руб , а ручка стоит 5 руб

 

Answer 2

Карандаш стоит 3 рубля ,а ручка 5 рублей!!!

5 карандашей 15 рублей ,а 2 ручки 10 рублей!!!

10+15=25 рублей!!!

Answer 3

Problem Analysis

We are given the information that a pencil and a pen together cost 8 rubles, and that 5 pencils and 2 pens together cost 25 rubles. We need to determine the individual prices of a pencil and a pen.

Solution

Let's assume the price of a pencil is x rubles and the price of a pen is y rubles.

From the given information, we can form two equations:

Equation 1: x + y = 8 (since the pencil and pen together cost 8 rubles) Equation 2: 5x + 2y = 25 (since 5 pencils and 2 pens together cost 25 rubles)

To solve this system of equations, we can use the method of substitution or elimination.

Method of Substitution

We can solve Equation 1 for x and substitute it into Equation 2:

From Equation 1, we have x = 8 - y.

Substituting this value of x into Equation 2, we get:

5(8 - y) + 2y = 25

Simplifying the equation:

40 - 5y + 2y = 25 -3y = -15 y = 5

Now, substituting the value of y back into Equation 1, we can find the value of x:

x + 5 = 8 x = 3

Therefore, the price of a pencil is 3 rubles and the price of a pen is 5 rubles.

Conclusion

Based on the given information, the pencil costs 3 rubles and the pen costs 5 rubles.