Question

Налистке бумаги прямоугольной формы длиной 12см и шириной 5см нарисован черный квадрат, сумма длин которого 20см. Найти площадь белой части листа.

Answer 1

Сначала найдем площадь листа.
S=12*5=60см в квадрате
теперь у квадрата.
У квадрата все стороны равны следовательно 20:4=5см
Sквадрата=5*5=25см в квадрате.
60-25=35см в квадрате, это площадь белой части листа.

Answer 2

Problem Analysis

We are given a rectangular sheet of paper with dimensions 12 cm by 5 cm. On this sheet, a black square is drawn, and the sum of its lengths is 20 cm. We need to find the area of the white part of the sheet.

Solution

To find the area of the white part of the sheet, we need to subtract the area of the black square from the total area of the sheet.

Calculating the Area of the Black Square

The sum of the lengths of the black square is given as 20 cm. Since the square has four equal sides, each side of the square can be calculated by dividing the sum of the lengths by 4.

Let's calculate the length of each side of the black square:

Length of each side of the black square = (Sum of lengths of the black square) / 4

Length of each side of the black square = 20 cm / 4

Length of each side of the black square = 5 cm

Now that we know the length of each side of the black square, we can calculate its area.

Area of the black square = (Length of each side of the black square) * (Length of each side of the black square)

Area of the black square = 5 cm * 5 cm

Area of the black square = 25 cm²

Calculating the Area of the White Part of the Sheet

To find the area of the white part of the sheet, we subtract the area of the black square from the total area of the sheet.

Total area of the sheet = (Length of the sheet) * (Width of the sheet)

Total area of the sheet = 12 cm * 5 cm

Total area of the sheet = 60 cm²

Area of the white part of the sheet = Total area of the sheet - Area of the black square

Area of the white part of the sheet = 60 cm² - 25 cm²

Area of the white part of the sheet = 35 cm²

Answer

The area of the white part of the rectangular sheet is 35 cm².