1?
how can a coin only lie on two coins cuz then the coin below will be lying on one coin
Is this solvable ??
Find no of ways by which we can stack 12 coins in a line so that each coin lies on table or on 2 coins
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UP 0 DOWN 0 0 12
12 Answers
1
24like this...here black coins are on table..and grey one is placed on top
1the ans. if u do
6C5 + 7C4 +8C3 + 9C2 +10 C1 +11C0
is 144 and not 154
and that seems to be the right ans. if the coins r identical
1i'm not getting the rite ans...i'm getting it as 274......i guess i've counted many combinations twice.....somebody pls correct me.....but , here's my approach
we v 12 coins....we place some of them in a line and the remainig in our hands, we place them on the coins on the table so as to satisfy the given condition....
so the combinations for (line,hand)={(12,0),(11,1)........(5,7)}...it ends here....u cant hv 4 on the line & then place the remaining
(12,0)-1
(11,1)-10
(10,2)-9C2
(9,3)-8C3+7
(8,4)-7C4+5*2+6*1*5
(7,5)-6C5+3*3+4+5*4C2
(6,6)-4
(5,7)-1+2
total=274
here's an illus for (7,5)
1this approach is wrong i think bcoz u cannot place a coin in a third row
then that coin does not lie on 2 coins but more than 2 coins