Question

A man takes a step forward with probability 0.4 and backward with

probability 0.6. Find the probability that at the end of eleven steps he is

one step away from the starting point.

Answer 1

hi. here is your answer...

either he took 6 forward steps and 5 backward steps or 6backward steps and 5 forward steps

reqd. probability

= 11C6 * (0.4)^6 * (0.5)^5 + 11C6 * (0.4)^5 * (0.6)^5

= 11C5 * (0.4)^5 * (0.6)^5 * (0.4 + 0.6) ... [11C6 = 11C5]

= (11x10x9x8x7)/(1x2x3x4x5) * (0.24)^5

= 0.368.