There are four banana, one strawberry and one water-melon smoothies, six in all.
Assuming all smoothies are identical when we pick, then the probability of picking a particular one is one divided by the total number (of smoothies).
Since there are four banana smoothies, the probability of picking a banana smoothie is four divided by six, or four-over-six, or two-thirds.
There are now five smoothies remaining, of which three are banana. Therefore the probability of picking another banana is three-over-five, or three fifths.
The final probability is the product of the individual (we call it a two-step experiment), or two-third multiplied by three-fifths, equal to two-fifths, or forty percent.
Recall that if the first banana smoothie had been put back in the batch, the probability would come out different.
