SSAT Elementary Level Math : How to find the probability of an outcome

Study concepts, example questions & explanations for SSAT Elementary Level Math

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Example Questions

Example Question #3 : Probability

Ten cards each have a number printed on them. Five have a 1 printed on them, three have a 2, and two have a 3. The cards are shuffled and a card is dealt. What is the probability that the card will not be a 3?

Possible Answers:

Correct answer:

Explanation:

There are ten cards total, and eight cards that are not threes. This makes the probability of drawing a three

Example Question #1 : Outcomes

If there are 2 blue marbles and 18 red marbles in a jar, what is the probability that Jeff will pick out a red marble?

Possible Answers:

Correct answer:

Explanation:

First, add the total number of marbles, which is . There are 18 red marbles, so you set up a fraction .

If you simplify by dividing the numerator and denominator by 2, you get .

Example Question #2 : Outcomes

A magician holds in his bag 3 green balls, 4 red balls and 7 blue balls. What is the probability of drawing a red ball from the bag?

Possible Answers:

Correct answer:

Explanation:

Probability = total number of possible outcomes/sample space.

                = 

                = 

Example Question #4 : Probability

Find the probability of an outcome. Express the outcome as fraction, reduced to its lowest terms.

Mr. Thomas went to a car lot to buy a new car. Of the 68 cars on the lot, 22 were black, 16 were silver, 8 were white, 12 were blue, and 10 were red.  What is the probability that Mr. Thomas will buy a blue car?

Possible Answers:

Correct answer:

Explanation:

To find the probability of an outcome, set up a fraction:

Since there are 12 blue cars (part) out of 68 cars in all (total possible) the fraction looks like this: 

If you reduce the fraction by 4 (because the numerator and the denominator are both divisible by 4 which makes 4 the GCF (greatest common factor), it becomes:

 

Example Question #3 : Outcomes

A bag of marbles contains  green marbles,  blue marbles, and  red marbles.

If  marbles are taken from the bag on each draw, what is the greatest possible amount of draws that can occur without drawing a red marble?

Possible Answers:

 draws

 draws

 draws

 draws

 draws

Correct answer:

 draws

Explanation:

There are  green marbles and  red marbles in the bag. Adding these amounts together gives  marbles in the bag that are not red. If all  of these were drawn before any red marble, this would require  draws at  marbles per draw (). Therefore, it is possible to draw up to  times without drawing a red marble.

Example Question #4 : Outcomes

Mikey has a box filled with cookies. He has 6 chocolate chip cookies, 4 sugar cookies, and 2 oatmeal raisin cookies. What is the chance that Mikey picks a sugar cookie out of the box?

Possible Answers:

Correct answer:

Explanation:

To find the probability of picking a sugar cookie from the bag of cookies, we need to set up a fraction like this:

 

The problem tells us that Mikey has 4 sugar cookies, so we can put that on the top of the fraction. The total number of cookies is equal to 6 chocolate chip cookies + 4 sugar cookies + 2 oatmeal raisin cookies, giving us a sum of 12 (which goes on the bottom of the fraction). That gives Mikey a  chance of picking a sugar cookie!

Example Question #5 : Outcomes

Sofia has a pizza pie with 8 slices. 4 slices have pepperoni, 3 slices have mushrooms and 1 slice has olives. If Sofia randomly picks a piece of pizza to eat, what is the chance that the slice of pizza has mushrooms on it?

Possible Answers:

Correct answer:

Explanation:

To find the probability of picking a mushroom slice from the pizza pie, we should set up a fraction like this: 

The problem tells us that we have 3 mushroom slices, so we can put that on the top of the fraction. The problem also tells us that we have 8 total slices in the pizza pie, so that can go on the bottom of the fraction. That gives Sofia a  chance of picking a mushroom slice!

Example Question #6 : Outcomes

Sarah, Mitch, and Ben are going to a concert. If they are seated in a row of , what fraction represents the probability Sarah will be seated in the middle of the row?

Possible Answers:

Correct answer:

Explanation:

The number of total possible arrangements of three items in a row is , or .

We can write out all the possible arrangments and count the number in which Sarah sits in the middle.

1) 

2) 

3) 

4) 

5) 

6) 

In  out of  possible arrangements, Sarah sits in the middle. Expressed as a fraction, this is , which is equivalent to .

Example Question #7 : Outcomes

Shannon has a box with 9 shirts inside. 4 shirts are pink, 3 shirts are yellow, 1 shirt is red, and 1 shirt is green. What is the probability that Shannon will randomly pick a pink shirt from the box?

Possible Answers:

Correct answer:

Explanation:

To find the probability of picking a pink shirt from the box, we need to set up a fraction: . The problem tells us that Shannon has 4 pink shirts, so we can put that on the top of the fraction. The total number of shirts is 9, which goes on the bottom of the fraction. That gives Shannon a  chance of picking a pink shirt from the box!

Example Question #8 : Outcomes

Tucker is going fishing at a local pond with 15 fish. 5 fish are tuna, 4 fish are salmon, 3 fish are yellowtail, and 3 fish are trout. What is the chance that the first fish Tucker catches will be a tuna or a trout?

Possible Answers:

Correct answer:

Explanation:

To find the probability of Tucker catching a tuna or a trout, we need to set up a fraction like this: . The problem tells us that there are 5 tuna and 3 trout in the pond, so we can put 8 on the top of the fraction. The total number of fish in the pond is 15, so that goes on the bottom of the fraction. That gives Tucker an 8/15 chance of catching a tuna or trout!

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