Shown below is the rectangle ABCD.
Given in cm:
AK = 5
DK = 4
The area of the rectangle is 24 cm².
Calculate the side AB.
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Shown below is the rectangle ABCD.
Given in cm:
AK = 5
DK = 4
The area of the rectangle is 24 cm².
Calculate the side AB.
Let's look at triangle ADK in order to calculate side AD:
Now let's substitute in our values:
We'll then move 16 to the other side and change the sign to the appropriate one:
Next, we'll take the square root and get:
Since AD is a side of rectangle ABCD, we can calculate side AB as follows:
Let's substitute in our values:
Finally, we'll divide both sides by 3:
8
Look at the rectangle ABCD below.
Side AB is 6 cm long and side BC is 4 cm long.
What is the area of the rectangle?
Because you need both dimensions of the rectangle to use Area = length × width. You only know the area (24 cm²) but need to find AD first using the Pythagorean theorem with triangle ADK.
Look for a right triangle where you know two sides and need the third. Here, triangle ADK is a right triangle with AK = 5 (hypotenuse) and DK = 4, so you can find AD.
In geometry problems, lengths are always positive. When you calculate , only use the positive value since we're measuring a physical distance.
The problem shows K on side DC of the rectangle, and diagonal AK creates a right triangle with the rectangle's sides. Rectangle corners are always 90°, making ADK a right triangle.
Yes! You could also use coordinate geometry by placing the rectangle on a coordinate plane, but the Pythagorean theorem approach is more direct and requires fewer calculations.
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