How to calculate the area of a rectangle whose length is 8 cm and perimeter 20 cm.

univerkov | January 11, 2021 | education

1) Find the width of the rectangle, knowing the perimeter and length.
The perimeter of a rectangle is the sum of the length and width of the rectangle multiplied by 2. Let’s write the formula:
P = (a + b) × 2,
where a is the length of the rectangle, b is the width.
Express the width of the rectangle from the formula for the perimeter:
P = 2a + 2b,
2b = P-2a,
b = (P-2a): 2.
Find the width of the rectangle by substituting the known values in the formula:
b = (20-2 × 8): 2 = (20-16): 2 = 4: 2 = 2 cm.
This means that the width of the rectangle is 2 cm.
1) Find the area of the rectangle.
The area of a rectangle is the product of the lengths of its sides. Let’s write the formula for the area:
S = a × b,
Let’s calculate:
S = 8 × 2 = 16 cm².
Answer: the area of the rectangle is 16 cm².

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