A rectangle has four straight sides and four corners. The two sides across from each other are always the same length. Every corner makes a right angle, which measures 90°.
A garden bed is drawn as a rectangle. One side is 7 cm, and the perimeter, the distance all the way round, is 24 cm. Opposite sides match, so half of 24 is one long side plus one short side: 12 cm. One of those two is the 7 cm side, so the other is 12 - 7 = 5 cm.
All four angles in a rectangle are always 90°, no matter how long or short the sides are. You never need to measure them to know that.
Area asks a different question: how much space is inside. Cover the same bed with 1 cm squares. It is 7 squares across and 5 squares down, so 7 × 5 = 35 square cm. That works backwards too. If you know the area and one side, divide to get the other side.
A rectangle's opposite sides are equal, every corner is 90°, and you can find a missing side using the perimeter or the area.
A rectangle is a four-sided shape with some very handy properties. Every corner of a rectangle is a right angle, which means it measures 90 degrees, like the corner of a book. Its opposite sides are always equal in length and parallel, so the two long sides match and the two short sides match.
These properties help you find missing numbers. The perimeter is the distance all the way around. You find it by adding all four sides, or with the shortcut: two times the length plus two times the width. If you know the perimeter and one side, you can work backwards to find the other side.
The area is the space inside the rectangle. You find it by multiplying the length times the width. If you know the area and one side, divide the area by that side to find the missing side.
The area of a rectangle tells you how many square units cover its surface. You find it by multiplying the length and the width.
So if a rectangle has an area of 24 square units, its length and width must multiply to 24. You can find every possible rectangle by listing pairs of whole numbers whose product is 24: 1 times 24, 2 times 12, 3 times 8, and 4 times 6. Each pair makes a different rectangle.
This also works backwards. If you know the area and one side, divide the area by that side to find the missing side. For example, if the area is 24 and one side is 6, the other side is 24 divided by 6, which is 4.
Area is the amount of space inside a flat shape. For a rectangle, finding the area is simple.
First, find the lengths of two sides that meet at a corner. Call one the base and the other the height. Because opposite sides of a rectangle are equal, you only need these two numbers.
Then multiply the base times the height. That product is the area, and it is measured in square units, like square centimeters or square inches. For example, a rectangle that is 5 centimeters long and 3 centimeters wide has an area of 15 square centimeters.
If you already know the area and one side, you can find the missing side by dividing the area by the side you know.
Square inches are a way to measure the area of a flat surface. One square inch is a square that is 1 inch on each side.
When your shape is a square or a rectangle, the job is easy. Measure the length of the shape in inches, then measure the width in inches. Remember that opposite sides of a rectangle are equal, so you only need to measure two sides that meet at a corner.
Multiply the length times the width, and the answer is the area in square inches. A rectangle that is 6 inches long and 4 inches wide covers 24 square inches. You can picture it as 24 little 1-inch squares tiling the whole surface with no gaps.
You have been sorting shapes by their corners, hunting for the square mark that means a right angle. Mia's plan for the new play area has a flower bed on it: a rectangle with one side 7 cm, and 24 cm of string all the way round.
Zara reaches for a ruler to measure the other three sides. What does the 7 cm side already tell you, before anybody measures anything?
اول این‌ها را یاد بگیر
این موضوع راه این‌ها را باز می‌کند
هنوز چیزی بر آن بنا نمی‌شود.
شغل‌هایی که بر این مهارت تکیه دارند. دنبال کردن یکی برای دیدن همهٔ چیزهایی که بر آن‌ها بنا شده است.
۲۰ سؤال پشت این درس منتظرند، هر کدام با پاسخ توضیح‌داده‌شده. هر پاسخ آسمان را پر می‌کند: ستاره‌ها هنگام یادگیری روشن می‌شوند و وقتی زمان برگشتن است کمرنگ می‌شوند.