A box contains 7 green, 4 red and 3 blue marbles. One marble is pulled from the box without looking, what is the probability of not getting a red marble?
Work:7+4+3=14
4/14=2/7
Or
7+3=10
4/10=2/5
Which one is correct.
Neither:
7+4+3=14
7+3=10
10/14 (or 5/7) marbles are not red
so you have about a 71% chance of not getting a red marble
To determine the probability of not getting a red marble, we need to find the number of favorable outcomes and divide it by the total number of possible outcomes.
First, let's calculate the total number of marbles in the box: 7 green + 4 red + 3 blue = 14 marbles.
Method 1:
To calculate the probability using this method, we count how many marbles in the box are not red. In this case, there are 7 green marbles and 3 blue marbles, so the number of favorable outcomes is 7 + 3 = 10.
Now, divide the number of favorable outcomes by the total number of possible outcomes: 10 / 14 = 5/7.
Method 2:
This method involves counting only green and blue marbles, without considering the total number of marbles in the box. In this case, there are 7 green marbles and 3 blue marbles, resulting in a total of 10 marbles that are not red.
Now, divide the number of favorable outcomes by the total number of outcomes: 10 / 10 = 1.
Out of the two methods you provided, the first method (4/14 = 2/7) is correct. This method considers the total number of marbles in the box, ensuring an accurate calculation of the probability.