There are 6 boxes numbered 1, 2, ... 6. Each box is to be filled up either with a red or a green ball in such a way that at least 1 box contains a green ball and the boxes containing green balls are consecutively numbered. The total number of ways in which this can be done is: Choose the correct choice from the following.
A) 5 B) 6 C) 21 D) 33 E) 60
6 Green - 1 way   5 green - 2 ways   4 green - 3 ways   3 green - 4 ways   2 green - 5 ways   1 green - 6 ways   total = &gt; 21 ways   Answer 21
<result>C</result>
There are 6 boxes numbered 1, 2, ... 6. Each box is to be filled up either with a red or a green ball in such a way that at least 1 box contains a green ball and the boxes containing green balls are consecutively numbered. The total number of ways in which this can be done is: