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Nigerian Senior Mathematics Olympiad Round 2
2021 Nigerian Senior MO Round 2
2
2
Part of
2021 Nigerian Senior MO Round 2
Problems
(1)
boxes and balls in a circle
Source: Nigerian Mathematics olympiad 2021 round 2 problem 2
2/14/2021
N
N
N
boxes are arranged in a circle and are numbered
1
,
2
,
3
,
.
.
.
.
.
N
1,2,3,.....N
1
,
2
,
3
,
.....
N
In a clockwise direction. A ball is assigned a number from
1
,
2
,
3
,
.
.
.
.
N
{1,2,3,....N}
1
,
2
,
3
,
....
N
and is placed in one of the boxes.A round consist of the following; if the current number on the ball is
n
n
n
, the ball is moved
n
n
n
boxes in the clockwise direction and the number on the ball is changed to
n
+
1
n+1
n
+
1
if
n
<
N
n<N
n
<
N
and to
1
1
1
if
n
=
N
n=N
n
=
N
. Is it possible to choose
N
N
N
, the initial number on the ball, and the first position of the ball in such a way that the ball gets back to the same box with the same number on it for the first time after exactly
2020
2020
2020
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combinatorics