Pet show has stations for each animal. There are 5 rabbits, 7 cats, 8 dogs, and 4 hamsters.

1. How many cats need to be added to make the probability 1/2.

For the probability to be 1/2, we need there to be 1 cat for every 2 animals. There are 5+8+4 = 17 other animals besides cats so we need to increase the amount of cats to 17 so that it is 1/2 of the total. We already have 7 so we need 17-7 = 10 more cats.

2. Assume we added the cats. What's the probability of picking a dog?

Since we added the cats, the total number of animals is now 17+17 = 34

There are 8 dogs, so the probability of picking a dog will be 8/34 which will reduce to 8/34 = 4/17 (you will pick 4 dogs every 17 attempts).

3. No more animals added. What is the probability of picking a rabbit or hamster?

Total rabbits and hamsters is 5+4 = 9 so there is a 9/34 chance of picking a rabbit or hamster. (you will pick a rabbit or hamster 9/34 attempts).

4. What is the probability of NOT picking a goldfish?

Be careful here... the question is what is the probability that you won't pick a goldfish? Well there are no goldfish, so there is a 34/34 (100%) chance that you won't pick a goldfish. You will NOT pick a goldfish 34 out of 34 times.

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3 years ago