Bunuel
What is the maximum number of nonoverlapping regions into which 3 lines can divide the interior of a circle?
(A) 4
(B) 6
(C) 7
(D) 8
(E) 9
Attachment:
regionscirc.png [ 7.94 KiB | Viewed 15993 times ]
In the diagram, one line makes two regions in the circle. 1 line adds one more region to the region already there (1 + 1 =2).
Two lines add two
more regions (to the 2 regions already there, 2 + 2 = 4)); 2 lines create 4 regions.
Three line add three
more regions (to the 4 regions already there, 4 + 3 = 7); 3 lines create 7 regions.
The pattern: Each Lth line adds L regions to the number of regions that already existed:
Line (+ line) --- Regions
1 (+ 1st line = adds 1 more region, 1+ 1 = 2) --> 2 regions
2 (+ 2nd line = adds 2 more regions, 2 + 2 = 4) --> 4 regions
3 ( + 3rd line = adds 3 more regions, 4 + 3 + 7) --> 7 regions
I cannot figure out a way to make 8 regions with three lines; and given the pattern, I think it is not possible.
Answer C
Navski , when I drew what you described, I counted six regions.