Question

Книга и блокнот вместе стоят 170 рублей, блокнот и ручка вместе стоят 50 рублей. Определите стоимость покупки, состоящей из книги, блокнота и ручки, если книга и ручка вместе стоят 140 рублей

Answer 1

Ответ:

книга -a

блокнот-b

ручка - c

a+b+b+c+a+c=170+50+140

2a +2b+2c= 360

a+b+c=360÷2=180 р стоят книга ,блокнот и ручка вместе

180-170= 10 р стоит ручка

180- 140= 40 р стоит блокнот

180- 50=130 р стоит книга

Answer 2

Problem Analysis

To determine the cost of purchasing a book, a notebook, and a pen, we need to use the given information about the prices of different combinations of these items. Let's break down the problem and solve it step by step.

Given Information

- The book and the notebook together cost 170 rubles. - The notebook and the pen together cost 50 rubles. - The book and the pen together cost 140 rubles.

Solution

Let's assign variables to the prices of the book, notebook, and pen. We'll use B for the book, N for the notebook, and P for the pen.

From the given information, we can write the following equations: 1. B + N = 170 (equation 1) 2. N + P = 50 (equation 2) 3. B + P = 140 (equation 3)

To find the cost of the book, notebook, and pen together, we need to solve these equations simultaneously.

Solving the Equations

To solve the equations, we can use a method called substitution. We'll solve equation 1 for B and substitute it into equations 2 and 3.

From equation 1, we have B = 170 - N.

Substituting this value of B into equations 2 and 3, we get: - (170 - N) + P = 140 (equation 4) - N + P = 50 (equation 5)

Now we have a system of two equations with two variables (N and P). We can solve this system to find the values of N and P.

Adding equations 4 and 5, we get: - 170 - N + N + P = 140 + 50 - P = 190 - N (equation 6)

Substituting the value of P from equation 6 into equation 5, we get: - N + (190 - N) = 50 - 190 = 50 + N - N = 190 - 50 - N = 140 (equation 7)

Substituting the value of N from equation 7 into equation 6, we get: - P = 190 - 140 - P = 50 (equation 8)

Now we have the values of N and P. To find the value of B, we can substitute the values of N and P into equation 1: - B + 140 = 170 - B = 170 - 140 - B = 30 (equation 9)

Final Answer

After solving the equations, we found that the cost of the book, notebook, and pen together is 30 + 140 + 50 = 220 rubles.

Please let me know if you need any further assistance!