Question 1088666
I can label those marbles so that I could tell them apart
(B1, B2, B3, will be the blue ones; W4, W5 the white ones).
There are {{{5*4/2=10}}} possible pairs of marbles
that I will be able to distinguish from one another
(representing {{{5*4=20}}} ordered pairs).
There is only {{{1}}} of those pairs made of two white marbles,
and there are only {{{3}}} of those pairs made of two blue marbles.
That is {{{1+3=4}}} pairs with matching marbles (same color).
The remaining {{{10-4=6}}} possible pairs of marbles
are made up of two marbles of different colors.
The possibility of that happening is {{{6/10=0.6="60%"}}} ,
because 6 of the 10 possible pairs of marbles were not matching colors.