Calculate Rectangle Perimeter: Finding the Border Length of EFCD (3×5)

Question

Look at the following rectangle:

What is the perimeter of the rectangle EFCD?

00:00 Calculate the perimeter of rectangle EFCD

00:03 Opposite sides are equal in a rectangle

00:11 The segment (ED) equals the entire side (AD) minus segment (AE)

00:16 Let's substitute appropriate values and solve for ED

00:31 This is the value of side ED, opposite sides in a rectangle are equal

00:42 Opposite sides in a rectangle are equal

00:55 The perimeter of the rectangle equals the sum of its sides

01:04 Let's substitute appropriate values and solve for the perimeter

01:28 And this is the solution to the question

Since in a rectangle every pair of opposite sides are equal to each other, we can claim that:

$BC=AD=5$

Now we can calculate side ED:

$AD-AE=ED$

Let's substitute the known data:

$5-3=ED$

$ED=2$

Side ED is equal to side FC and therefore it is also equal to 2

We can also claim that:

$AB=CD=EF=7$

Now we can calculate the perimeter of rectangle EFCD:

$2+7+2+7=4+14=18$