Question

Given parallelogram ABCD, m\angle A=5x+18 and m\angle B=3x-6 find find m\ C

Answer 1

57

Explanation:

Firstly, we will need to calculate what x is.

To calculate this, the important property of the parallelogram to use is that adjacent angles are supplementary.

This means A and B are supplementary while B and C are also supplementary

what we are trying to say is that they add up to be 180

Thus,

5x + 18 + 3x -6 = 180

8x +12 = 180

8x = 180-12

8x = 168

x = 168/8

x = 21

Thus, the measure of angle B is 3x-6 = 3(21) -6 = 63-6 = 57

Now, another important property of parallelograms is that opposite angles are equal. This means that angle B= C = 57