# Supplemenary angles 2x+8 and x-24 add up to 179.99 degrees but they must add up to 180 degrees.  What do I do?

samhouston | Middle School Teacher | (Level 1) Associate Educator

Posted on

Since the angles are supplementary, they must add up to 180 degrees.

2x + 8 + x - 24 = 180

3x - 16 = 180

3x = 196

x = 65.33

2(65.33) + 8 + 65.33 - 24 = 179.99

You got 179.99 because of rounding.  The variable x does not actually equal 65.33 because the 3 is a repeating decimal.  Instead of rounding, use the fraction 196/3.  This is equal to 65.333333333333.... etc...  Now try checking.

2(196/3) + 8 + 196/3 - 24 = 180

Without rounding, you get the required answer of 180 degrees.

I hope this helped!  :)

jerveelim | College Teacher | (Level 1) Honors

Posted on

Numerically speaking, 179.99 can be rounded off to 180. In this case, you can add up (2x+8) + (x-24)= 179.99

so, you can have 3x-16=179.99

this will give 65.33 as the value of x

On the other hand, if you use (2x+8) + (x-24) = 180, you will get 65.3333333333 as the value of x.

Following the rules in rounding off, this value will be 65.33, the same answer for 179.99

In addition, if you will follow the rules in significant figures, in either value (179.99 or 180), you will simply get 65

mathematics11 | eNotes Newbie

Posted on

Thank you.  :)  I knew that the variable x wasn't exactly 65.33 because it is a repeating decimal but I still don't see how it can be 180.  I don't mean to seem obtuse but to me to get 180 degrees you have to round 179.99 up to 180.