Thread: A probability problem

A WiFi server X transmitted messages to the outside world via two 1/O devices, A and B. X's traffic shaping mechanism sent 70% of messages via A and the rest via B. If the routes A and B have 25% and 10% of retransmissions, what is the reliability of X in terms of the number of trials to get a transmission success?
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My answer is:
( 70% x ( 1-25% ) ) + ( 30% x ( 1-10% ) ) = 0.795
So, it needs 0.795 trial to get a transmission success.

Is it correct? I am not sure for the answer, could anyone verify it for me, pls.
Thank you!!

I'm assuming you mean the expected number of trials to get a transmission success.

The number of transmissions required a successful transmission can be modeled as a geometric distribution with success probability p = 0.795 as calculated by you. Then the expected number of transmission required for a successful transmission is 1/p = 1.258