Question

Figure CDEF is a parallelogram. What is the value of r? 2 3 4 5

Answer 1

Answer:

5

Step-by-step explanation:

Opposite sides of parallelograms are congruent.  This means that the measure of FC, 10r-20, and the measure of DE, 6r, are equal.  This gives us the equation

10r-20 = 6r

Subtract 10r from each side:

10r-20-10r = 6r-10r

-20 = -4r

Divide both sides by -4:

-20/-4 = -4r/-4

5 = r

Answer 2

Given that figure CDEF is a parallelogram.

A parallelogram is a quadrilateral with two pairs of parallel sides. The opposite sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure.

Using the property of a parallelogram which says that the length of any two opposite sides are equal. We have:

CF = DE
10r - 20 = 6r
10r - 6r = 20
4r = 20
r = 20 / 4
r = 5