Both Tetsuya and Mason are interested in finding the probability that a red marble will be chosen out of the bag. We will decide if either of them is correct.
Let's first analyze Tetsuya calculations. He wants to use the theoretical probability.
P(R)= Favorable Outcomes/Possible Outcomes
The number of favorable outcomes is the number of red marbles in the bag, so it is equal to 4. The number of possible outcomes is the number of all marbles in the bag. Let's find it.
4+7+5+2 = 18
We have enough information to find the probability that a red marble will be chosen P(R).
P(R)= 4/18
We see that Tetsuya used the wrong number of possible outcomes in the denominator. Let's look at Mason's solution. They wanted to use the probability of complementaryevents. However, they found the probability that a selected marble is not red.
1 - 4/18
They subtract 418, which is the probability that a red marble will be chosen. Therefore, none of them gave the correct answer.
