Answer: 2/5
Explanation: P(red) means the probability of picking a red marble out of the jar and we can find this by using the ratio for the probability of an event which is number of favorable outcomes/total number of outcomes.
Since there are 8 red marbles in the jar, the number of favorable outcomes is 8 and since there are 20 marbles in all and it's equally likely that we will choose any of the marbles, the total number of outcomes is 20.
Therefore, the probability of choosing a red marble is 8/20.
Notice however that 8/20 is not in lowest terms so we need to divide the numerator and denominator of 8/20 by their greatest common factor of 4 to get 2/5. So our final answer for the probability of choosing a red marble is 2/5.
