SOLUTION: The interior angles of a convex nonagon have degree measures that are integers in arithmetic sequence. What is the smallest angle possible in this nonagon? A.) 144º B.) 104º

Algebra ->  Polygons -> SOLUTION: The interior angles of a convex nonagon have degree measures that are integers in arithmetic sequence. What is the smallest angle possible in this nonagon? A.) 144º B.) 104º       Log On


   



Question 1132061: The interior angles of a convex nonagon have degree measures that are integers in arithmetic sequence. What is the smallest angle possible in this nonagon?
A.) 144º
B.) 104º
C.) 96º
D.) 108º
E.) 112º
Note: if you figured out the smallest angle, please give the rest of the 8 angles so I can see the arithmetic sequence. Thank you!!

Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

First, determine what the total degrees for a nonagon is
180+%2A+%289+-+2%29+=>
180+%2A+7+=>
1260+
1260+=+t%5B1%5D+%2B+t%5B2%5D+%2B+t%5B3%5D+%2B+t%5B4%5D++ ... + t%5B9%5D+
1260+=+t%5B1%5D+%2B+t%5B1%5D+%2B+d+%2B+t%5B1%5D+%2B+2d++ ... + t%5B1%5D+%2B+8d+
1260+=+9+%2A+t%5B1%5D+%2B+d+* (1+%2B+2+%2B+3 + ... ++8)
1260+=+9+%2A+t%5B1%5D+%2B+d+%2A+36+
1260+=+9+%2A+%28t%5B1%5D+%2B+4d%29+
140+=+t%5B1%5D+%2B+4d+

So the 5th term will be 140 degrees
Since it's convex, then all of the angles will be greater than 90 degrees
t%5B1%5D+%3E+90+
140+-+4d+%3E+90+
140+-+90+%3E+4d+
50+%3E+4d+
12.5+%3E+d+
So the greatest integer value d can be is 12+
140+-+4+%2A+12+=+92+
Technically the answer is 92+
92+%2B+104+%2B+116+%2B+128+%2B+140+%2B+152+%2B+164+%2B+176+%2B+188 =>
280+%2B+280+%2B+280+%2B+280+%2B+140+=>
140+%2A+9 =>
1260+

since there is no choice for 92+, we have
140+-+4d will be our first angle

d+=+11+
140+-+44+=+96+
=> 96+is the smallest answer in the available answer set

so, your answer is: C.) 96º


Answer by ikleyn(52873) About Me  (Show Source):
You can put this solution on YOUR website!
.

            The solution by  @MathLover1 is   I N C O R R E C T.

            It is   T O T A L L Y   W R O N G,   to be precise.


This problem came to the forum  2-3  days ago,  and I correctly solved it under this link

https://www.algebra.com/algebra/homework/Polygons/Polygons.faq.question.1132033.html

https://www.algebra.com/algebra/homework/Polygons/Polygons.faq.question.1132033.html