Question

The numbers 1-4 are each written on an index card. The 4 cards are put into a bag and 2 of them are drawn at random. What is the probability that the sum of the two cards drawn are greater than 5? I actually know the answer to this question (1/3), however, I don’t know how to solve it; please include an explanation.

Answer 1

Explanation:

Write a list of all possible outcomes

1-2

1-3

1-4

2-1

2-3

2-4

3-1

3-2

3-4

4-1

4-2

4-3

There are 12 possible outcomes. How many of them have totals of 6 or 7

I count 4

So the probability is 4/12 = 1/3, just as you said.

Is there an easier way?

You might be able to get the 12 easier.

You have 4 choices for the first number and 3 for the second.

P(12) = 4*3 = 12

Getting 6 or 7 might be somewhat trickier.

4 and 3 make seven. That gives two ways 4-3 and 3-4

4 and 2 make six. That gives 2 more ways 4-2 and 2-4

That's all that's possible.

answer: 4 ways make success. The total number of ways is 12.