Question

a school photocopier has a 95% chance of working on any particular day. Draw a tree diagram showing the possibiltiies for the working or otherwise of the photocopier over 2 consecutive days. Hence, determine the likelihood that it will be working on at least one of these days.

Answer 1

Here is current diagram:

first day& second day

& & work(0.95)
/
work(0.95)& &
& / \
& /& & no work(0.05)
/
\& work(0.95)
& \& /
& no work(0.05)
& \
& no work(0.05)

So, the probability that a school photocopier will be working on at least one of two consecutive days is
P = 0.95*0.95 = 0.95² = 0,9025.