Summer Clouds moderators
07/11/2017 at 11:16-
If this person start go:
- At first door, he/she can exit at 6 rest doors
- At second door, he/she can exit at 5 rest doors
- At third door, he/she can exit at 4 rest doors
- At fourth door, he/she can exit at 3 rest doors
- At fifth door, he/she can exit at 2 rest doors
- At sixth door, he/she can exit at 1 rest doors
- And at last door, he/she can exit at 0 rest doors
So this person will have:
6 + 5 + 4 + 3 + 2 + 1 + 0 = 21 [ways]
Selected by MathYouLike