Mr. Sibbal walk up 16 steps, going up either 1 or 2 steps with each stride there is explosive material on the 8 th step so he cannot step there. Then number of ways in which Mr. Sibbal can go up.
Text Solution
Verified by Experts441
(441)
Sol. x number of 1 unit steps
y number of 2 unit steps
x + 2y = 7
x = 7 y = 0 Number of ways = 1
x = 5 y = 1 Number of ways = 6
x = 3 y = 2 Number of ways = 10
x = 1 y = 3 Number of ways = 4
Total number of ways = 21 ways
Now he cannot go on 8 th step. Now he reach 9 th step in 1 ways and then again move from 9 th to 15 th steps
x + 2y = 7
Number of ways = 21
Total number of ways = 21.21 = 441
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