Calculate the value of B_6?

Logic Level 2

Let A n denote the number of all n− digit positive integers formed by the digits 0,1 or both such that no consecutive digits in them are 0 and B n denote number of such n Digit integers ending with digit 1 and C n denote number of such n Digit integers ending with digit 0. Then the value of B 6 is?

11 9 8 7

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1 solution

Parth Sankhe
Oct 12, 2018

The first and last digit will have to be 1. The middle 4 digits have to be filled with 0 and 1

Let 1s be Xs and 0s be Ys

4X, 0Y = 1 way (1 1 1 1)

3X,1Y = 4 ways(1 1 1 0, 1 1 0 1, 1 0 1 1, 0 1 1 1)

2X, 2Y = 3 ways (1 0 1 0, 0 1 0 1, 0 1 1 0)

Note that there can't be 3 or more 0s as there will be no way to keep them non-adjacent.

Therefore, a total of 8 ways.

Note that B n B_n is the Fibonacci number F n F_n

Otto Bretscher - 2 years, 8 months ago

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Oh yeah, cool!

Parth Sankhe - 2 years, 7 months ago

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