AB=25

DC=5x

AD=y+5

BC=2y

Quadrilateral ABCD is a parallelogram if both pairs of opposite sides are congruent. Show that quadrilateral ABCD is a parallelogram by finding the lengths of the opposite side pairs.

A) 10,5

B) 25,10

C) 25,15

D) 50,20

Answer: B

First, we have to find the values of the variables.

AB = DC, so 25 = 5x.

25/5 = 5, so x = 5

AD = BC, so 2y = y + 5.

Subtract y from both sides:

y = 5

Now we know both x and y equal 5.

AB and BC are adjacent, so we can use those two.

AB = 25

BC = 2 (5) = 10

Option B is the correct answer