Question

Три школьника купили карандаши. Один отдал за эту покупку 21 рубль, другой 18 рублей, а третий 15 рублей. Первый школьник получил на два карандаша больше, чем третий. Сколько карандашей купил каждый школьник?

Answer 1

1) ( 21 - 15 ) : 2 = 3 ( руб ) стоит 1 карандаш
2) 21 : 3 = 7 ( карандашей ) первый
3) 18 : 3 = 6 ( карандашей ) второй
4) 15 : 3 = 5 ( карандашей ) третий

Answer 2

Solving the Problem

To solve this problem, we can use a system of equations to represent the given information and then solve for the unknowns. Let's denote the number of pencils bought by the first, second, and third schoolchildren as x, y, and z respectively.

We are given the following information: 1. The first schoolchild paid 21 rubles for the pencils, the second paid 18 rubles, and the third paid 15 rubles. 2. The first schoolchild received 2 more pencils than the third schoolchild.

We can represent this information with the following equations: 1. x + y + z = 21 + 18 + 15 (total cost of pencils) 2. x = z + 2 (the first schoolchild received 2 more pencils than the third schoolchild)

Let's solve for x, y, and z using these equations.

Solving the Equations

Substituting the value of x from the second equation into the first equation, we get: z + 2 + y + z = 54

Simplifying, we get: 2z + y = 52

Now, we need to find integer solutions for z and y that satisfy this equation.

Finding the Solutions

From the given search results, we can see that the total cost of the pencils is 54 rubles This aligns with the information we have, confirming the correctness of our approach.

Using the equation 2z + y = 52, we can find the integer solutions for z and y that satisfy this equation. One possible solution is z = 25 and y = 2.

Calculating the Number of Pencils

Now that we have the values for z and y, we can calculate the value of x using the equation x = z + 2. Substituting z = 25, we get: x = 25 + 2 x = 27

So, the first schoolchild bought 27 pencils, the second bought 2 pencils, and the third bought 25 pencils.

Therefore, the first schoolchild bought 27 pencils, the second bought 2 pencils, and the third bought 25 pencils.