A bag contains 5 blue marbles and 5 red marbles. If marbles are NOT replaced after being selected from the bag, what is the probability (in percentage) of picking 2 red marbles? Give your answer to one decimal place.

As there are a total of 10 marbles in the bag, then the probability of picking a red marble is 5/10. When the next marble is selected, there are only 9 marbles left in the bag since the red marble has not been replaced. As there are only 4 red marbles left, the probability of picking another red marble is 4/9. To get the total probability, these two individual probabilities can be multiplied to give 20/90 which can be reduced to 2/9. As the question asks for this fraction to be given as a percentage to one decimal place, calculate 2/9 on your calculator and then multiply by 100 to give 22.2%.