Question

В коробке 42 карандаша. Сколько карандашей каждого цвета, если зелёных и жёлтых 35 карандашей, а жёлтых и красных 28 карандашей? (решение по действиям)

Answer 1

42-35=7-это нашли красных
42-28=14-это нашли зеленых
14+7=21-это нашли красные и зеленые вместе
42-21=21-это нашли желтые
Ответ: желтых-21, зеленых-14, красных-7

Answer 2

Problem Analysis

We are given a box containing 42 pencils. We need to determine the number of pencils of each color if there are 35 green and yellow pencils, and 28 yellow and red pencils.

Solution

Let's assume the number of green pencils is x, the number of yellow pencils is y, and the number of red pencils is z.

From the given information, we can form the following equations:

1. x + y = 35 (equation 1) 2. y + z = 28 (equation 2) 3. x + y + z = 42 (equation 3)

To solve these equations, we can use substitution or elimination method. Let's use the elimination method.

Adding equation 1 and equation 2, we get:

(x + y) + (y + z) = 35 + 28 x + 2y + z = 63 (equation 4)

Subtracting equation 3 from equation 4, we get:

(x + 2y + z) - (x + y + z) = 63 - 42 x + 2y + z - x - y - z = 21 y = 21

Now, we can substitute the value of y in equation 1 to find the value of x:

x + 21 = 35 x = 35 - 21 x = 14

Similarly, we can substitute the value of y in equation 2 to find the value of z:

21 + z = 28 z = 28 - 21 z = 7

Therefore, there are 14 green pencils, 21 yellow pencils, and 7 red pencils in the box.

Answer

There are 14 green pencils, 21 yellow pencils, and 7 red pencils in the box.

Explanation

The solution to the problem is obtained by solving the system of equations formed from the given information. By substituting the value of y in equation 1, we find that there are 14 green pencils. Similarly, by substituting the value of y in equation 2, we find that there are 7 red pencils. The value of y is determined to be 21, which represents the number of yellow pencils.