# Math Help - Urgent Help Please

I really need help with this question, I have to present the answer and how to do it in front of my class tomorrow. If someone can please help me with as much detail as possible I would really appreciate it.

Thanks.

2. Hello, juvenilepunk!

26. If two opposite angles of a quadrilateral measure 120°,
and the measure of the other angles are multiples of 10°,
what is the probability that the quadrilateral is a parallelogram?

Since $\angle A = \angle C = 120^o$, then: . $\angle B + \angle D \:=\:120^o$

Since $\angle B\text{ and }\angle D$ are multiples of 10°, there are 11 cases.

. . $\begin{array}{c|c} B & D \\ \hline
10 & 110 \\ 20 & 100 \\ 30 & 90 \\ 40 & 80 \\ 50 & 70 \\ {\color{blue}60} & {\color{blue}60} \\ 70 & 50 \\ 80 & 40 \end{array}$

. . $\begin{array}{c|c} 90 & \;30 \\ 100 & \;20 \\ 110 & \;10 \end{array}$

In only one case the quadrilateral is a parallelogram.
Code:
          A * - - - - - - - - - * B
/ 120°          60° /
/                   /
/                   /
/                   /
/ 60°          120° /
D * - - - - - - - - - * C

Therefore: . $P(\text{parallelogram}) \;=\;\frac{1}{11}$

3. This helps so much, thanks.