All ACT Math Resources
Example Questions
Example Question #191 : Data Analysis
Six lightning rods are set up around key buildings in an office complex. The odds of lightning striking any one of them are roughly equal, with a seventh option (equally likely as any of the others) being that the lightning strikes anything else instead, like a tree or plane.
What are the odds that the next three lightning strikes all hit different lightning rods?
To calculate the odds of a chain of events, multiply the events' probabilities together. Since we want the lightning to strike any rod target on the first bolt, our odds of success are . The next bolt cannot hit the non-rod target nor the target that was already struck, so our chances are now . The last bolt cannot strike either of the previous two targets or the ground, so our odds drop further to . Multiply these individual probabilities to get the probability of this chain of events:
Example Question #192 : Data Analysis
The odds of guessing a question right on a particular test are . Connell guesses on all ten questions on the test, and gets a score of . What were the odds of this score?
To find the odds of a particular chain of outcomes, find the product of the odds of each required step's outcomes.
In this case, we can assume that Connell got the first three questions right (in other words, the order doesn't matter since it doesn't noticeably bias the later results).
So the odds of this are:
The odds of getting a problem wrong with a blind guess, on the other hand, is , so the next seven questions being wrong have an odds of:
Lastly, multiply our two individual probabilities together:
Thus, the odds of getting this exact result are
Example Question #79 : How To Find The Probability Of An Outcome
Jeremy has three coins. Each of the coins have a tails and heads side. If Jeremy flips all three coins, what is the probability that Jeremy gets tails on all three coins?
This is a probability problem. What you must first decide is what is the probability of getting the outcome you want?
The probability of getting tails on each of the three coins is or .
Since we have three coins, we multiply their individual probabilities to get the final answer:
.
Example Question #71 : How To Find The Probability Of An Outcome
In a bag, there are 5 green marbles, 8 blue marbles, and 7 red marbles. What is the probability of pulling out a blue marble.
To find probability, you must take the # of desired outcomes divided by the total. Thus,
Example Question #81 : How To Find The Probability Of An Outcome
A certain pet store has What is the probability that a person chooses a cat from the pet store?
Probabilities can be found by the following equation: , where the total outcomes is the sum of all of the different number of pets, and the numinator is the number of pets we want to pick (there are only cats). In our case, the probability is simply .
Example Question #82 : How To Find The Probability Of An Outcome
dogs are competing to become Best in Show. How many possible outcomes are there for the dogs to win prize if they cannot win more than one prize?
This is a combination problem. The solution to the question can be found by considering how many dogs can win the first prize (all five of them)! Then, if one has already won a prize, how many can win the second prize (four). This is because one of the five dogs has already been awarded a prize. Then, how many options are left to win the third prize? The answer is three. In a combination problem, we always multiply all of the possible outcomes for the results to get a total possible outcome value:
Example Question #81 : Probability
Aaron, Gary, Craig, and Boone are sitting down in a row of four chairs. What is the probability that Aaron and Gary will be seated beside each other?
Consider first all of the possible ways the men may be arranged, which is
Now, consider all of the ways that Aaron and Gary could be seated beside each other; it may be easier to visualize by drawing it out:
- A G _ _
- G A _ _
- _ A G _
- _ G A _
- _ _ A G
- _ _ G A
As seen, there are six possibilities.
Finally, for each of these cases, Craige and Boone could be seated in one of two ways.
So the probability that Aaron and Gary will be seated beside each other is:
Example Question #81 : Probability
Of 252 applicants, 9 received scholarships. What is the ratio of applicants that received a scholarship to those who did not?
1:28
1:27
1:9
1:25
1:27
243 applicants did not get a scholarship. This ratio is 9:243, which reduces to 1:27.
Example Question #81 : How To Find The Probability Of An Outcome
A bag contains 6 yellow marbles, 5 red marbles, 4 blue marbles, and 3 green marbles. If John randomly selects a marble from the bag, what is the probability that he selects a marble that is neither red nor blue?
Probability is the likelihood that an outcome will occur, and it is calculated by dividing the number of favorable events by the total number of possible events that may occur. In order to answer the question, we need to divide the number of non-red and non-blue marbles (i.e. the number of favorable events) by the total number of marbles in the bag (i.e. the total number of possible events). The total number of non-red, non-blue marbles is the same as the number of yellow and green marbles
Example Question #82 : Probability
Caroline is given instructions to plant five different flowers in a specific order in a garden. When she goes to plant the flowers, Caroline can only remember which flowers are to be planted in the first two positions in the garden, and she cannot remember which flowers to plant in the last three positions in the garden. If Caroline plants the first two flowers correctly, and then randomly plants the last three flowers, what is the probability that Caroline has planted all of the flowers in the correct order?
If the flowers that go in the first two locations are already determined, there are only three positions that run any risk of having the wrong flower planted in them. First, determine the number of possible ways in which Caroline can finish planting the garden. There are 3 possible flowers that she could plant in the third position. After she plants a flower there, there will be 2 flowers she can plant in the fourth position. After planting a flower in the fourth position, there will be only one flower left to plant in the fifth position; therefore, the number of possible ways she could finish the garden is:
There are 6 possible outcomes. Only one of these outcomes will be successful; thus, the probability that Caroline finishes planting the garden in the correct order is one out of six: