A certain diner has parallel parking along the street. Being so popular with mot
ID: 3121308 • Letter: A
Question
A certain diner has parallel parking along the street. Being so popular with motorcyclists, the
parking spots are marked to accommodate the length of a motorcycle. A car can also park there,
and ts just right in two consecutive spots.
Explanation / Answer
Let tn be the number of ways in which n motor cycle spaces can be filled with cars and motor cycles.
therefore, t1 = (m) =1, t2 = (m,m), (cc) = 2, t3 = (m,m,m),(cc,m),(m,cc) =3.
In a similar way, we have t4= 5, t5= 8.
From the above statements, we can write,
t1=1, t2 =2
t3 = t2 + t1
t4 = t3+t2
t5= t4+t3
......
........
tn = tn-1 + tn-2.
now consider there are n+2 spaces to park the vehicles. If the last space is filled by a motorcycle, then the remaining n+1 spaces can be filled in tn+1 ways. Similarly if the last two spaces are filled by a car, the remaining n spaces are occupied by tn ways.
Therefore tn+2 = tn+1 + tn.
This is true for any value of n.
Hence {tn} =1 for n=1,
{tn} = 2 for n=2
{ tn} = tn-1 + tn-2, for n >2.
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