John is twice as old as Bill. Greg is 7 years older than Bill. Four years ago, the sum of their ages was 55. How old is Greg?
1 answer:
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Answer:
The probability is 0.4909
Step-by-step explanation:
The following equation for nCk give as the number of ways in which we can select k elements from a group of n elements:
Then, there are 220 ways in which we can select 3 candies from the 12 that are in the pack. It is calculated as:
On the other hand, there are 108 different ways to select the 3 candies in which they are all different flavors. It is calculated as:
4C3 * 3C1 * 3C1 * 3C1 = 108
Because, 4C3 give us the number of ways to select 3 flavors from the 4 flavors. From this 3 flavors selected, we are going to select one candie from each one, so we multiply 3 times by 3C1, one for each flavor.
Finally, the probability is the division between the number of ways in which we can select 3 candies with different flavors and the total number of ways in which we can select 3 candies from the 12 in the pack. This is: