What is the probability of drawing two blue marbles if the first marble is placed back in the bag before the second draw

We want to work out the probability of choosing a blue marble, and then choosing another blue marble:

P(choosing blue marble) and P(choosing blue marble)

in probability, and means times.

So

P(choosing blue marble) x P(choosing blue marble)

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In total there are 10 marbles, and 5 are blue. So the probability of choosing a blue marble is

So:

P(choosing blue marble) x P(choosing blue marble)

= x

=        (this can simplify)

=

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Answer