
 Math Is Fun Forum / help !!! 
  The other two angles can combine with one of the angles in the inner pentagon to make a straight line. 
  This means that angle A is 180°  ((180°  p) + (180°  q)), which is equal to p + q  180° (where p and q are the appropriate angles in the pentagon). 
  Similar reasoning can be applied to B, C, D and E, and so if we label the inner angle of the pentagon as p, q, r, s and t, then the total of A, B, C, D and E is found by 2(p+q+r+s+t)  900°. 
 www.mathsisfun.com /forum/viewtopic.php?pid=49523 (742 words) 
