   SEARCH HOME Math Central Quandaries & Queries  Question from dolly, a student: having a time-with equations inequalities and problem solving the sum of the measure of the angles of a parallelogram is 360.angles a) a and d , have the same measure as angle c and d, c is twice the measure of angle a, what is the angle for each. Hi Dolly,

You have named the angles a, b, c and d. I am going to use capital letters to represent the measures of the angles

The measure of the angle a is A.
The measure of the angle b is B.
The measure of the angle c is C.
The measure of the angle d is D.

Now look at the information in the problem and write it in terms of the letters A, B, C and D.

the sum of the measure of the angles of a parallelogram is 360.angles

A + B + C + D = 360

I think the next statement should be

a and d have the same measure and b and c have the same measure

A = D
B = C

c is twice the measure of angle a

C = 2A

Now put this information together. If A = D and B = C then the first equation can be written

A + B + C + D = A + C + C + A = 2A + 2C = 360

In the equation you have now, 2A + 2C = 360, you can substitute C for 2A. Solve the resulting equation for C.

I hope this helps,
Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.