asked 175k views
1 vote
The tickets in a box are numbered from 1 to 15 inclusive. If a ticket is drawn at random and replaced and then a second is drawn at random, what is the probability that the sum of their numbers is even?

a. 49/225
b. 1/2
c. 113/225
I think it is c but I don't know...

asked
User Leighton
by
8.0k points

1 Answer

4 votes
We know that two odd numbers make an even number and two even numbers make another even number. So out of the first choice you have a 7/15 chance of getting it even and an 8/15 chance of getting it odd.

If you get the first one even, then the second one MUST also be even so you multiply 7/15 with itself.

If you get the first one odd, then the second one MUST also be odd so you multiply 8/15 with itself as well.

You should have:

(7/15) x (7/15)

and

(8/15) x (8/15)

By multiplying the top portions with each other and the bottom portions with each other you get:

49/225 and 64/225 respectively.

Add both fractions together to get your answer.

Your answer should be (64+49)/225 = 113/225

Your answer is 113/225.

Well, it seams as if you were correct. The answer is c. 113/225. Hope this helped!

Answer: c. 113/225

answered
User Boanerges
by
8.0k points

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