Question

4 карандаша и 3 тетради стоят 34 руб., 2 карандаша и 2 тетради стоят 20 руб. сколько будет стоить 8 карандаша и 7 тетрадей?

Answer 1

4к+3т=34 
2к+2т=20 
2*(к+т)=20 :(2) 
к+т=10 
к=10-т 
4*(10-т)+3т=34 
40-4т+3т=34 
-т=34-40 
-т=-6 (:-1) 
т=6 руб 
к=10-6=4руб 

8к*4руб+7т*6руб=32руб+42руб=74руб




4 карандаша и 3 тетради - 34руб.
2 карандаша и 2 тетради - 20руб.
Соответственно:
8 карандашей и 7 тетрадей = 34+20+20=74руб.

Answer 2

Problem Analysis

We are given the prices of 4 pencils and 3 notebooks, as well as the prices of 2 pencils and 2 notebooks. We need to find the total cost of 8 pencils and 7 notebooks.

Solution

Let's assign variables to the prices of pencils and notebooks: - Let's say the price of one pencil is p. - Let's say the price of one notebook is n.

According to the given information, we have the following equations: - 4p + 3n = 34 (Equation 1) - 2p + 2n = 20 (Equation 2)

To find the cost of 8 pencils and 7 notebooks, we need to solve for p and n and then calculate the total cost.

Solving the Equations

We can solve the system of equations (Equation 1 and Equation 2) to find the values of p and n.

To eliminate n, we can multiply Equation 2 by 3 and Equation 1 by 2, and then subtract Equation 2 from Equation 1:

2(4p + 3n) - 3(2p + 2n) = 2(34) - 3(20) 8p + 6n - 6p - 6n = 68 - 60 2p = 8 p = 4

Now, we can substitute the value of p into Equation 2 to find n:

2(4) + 2n = 20 8 + 2n = 20 2n = 20 - 8 2n = 12 n = 6

Therefore, the price of one pencil (p) is 4 rubles and the price of one notebook (n) is 6 rubles.

Calculating the Total Cost

Now that we know the prices of pencils and notebooks, we can calculate the total cost of 8 pencils and 7 notebooks:

Total cost = (8 * price of one pencil) + (7 * price of one notebook) Total cost = (8 * 4) + (7 * 6) Total cost = 32 + 42 Total cost = 74 rubles

Answer

The total cost of 8 pencils and 7 notebooks is 74 rubles.