Answer:
a) 13/25
b) 12/15
Step-by-step explanation:
a) Since it is with replacement, the chance of them being both the same colour will be
P(both red) + P(both black) = (6/15*6/15) + (9/15*9/15)
= 13/25
b) If they are both different colours, then we will be working out
P(both colours) = (6/15*9/15)*2 = 12/25 (Its *2 because the other way of pulling both colours is 9/15*6/15 which is the same but flipped)
Another way of working this question out is
P(1-All red or all blue) which from above we know that All red or all blue is 13/25 so
P(1-All red or all blue) = 1 - 13/25 = 12/25
