ACT Math : ACT Math

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #82 : Outcomes

Jane bought 30 pens, 9 of which had black ink, 10 blue ink and 11 red ink. On her way home from the store all the pens got mixed together and 2 blue pens were lost. When Jane arrives home she reaches into the bag and randomly picks a pen. What is the probability that she picks a blue pen?

Possible Answers:

Correct answer:

Explanation:

When Jane starts she has a total of 30 pens, 9 black, 10 blue and 11 red. Two of the blue pens were lost. This dropped the number of blue pens to 8 and the total count of pens to 28.

To find the probability of something happening, take the total amount of things in question, the blue pens or 8, and compare them to total amount of pens which is now 28 pens.

 chance to draw a blue pen from the bag.

*The pitfall for these types of questions is to realize that not only does the count of blue pens decrease but also the total count of pens. Make sure to adjust both values. 

Example Question #83 : Probability

A spinner has the numbers 1 through 10 placed on a circle. What is the probability that the spinner lands on a number divisible by 3 on one spin?

Possible Answers:

Correct answer:

Explanation:

To find the probability of an event, find the number of ways that even could happen divided by the total number of outcomes of the event.

Number of ways we could spin a number divisible by 3: 
3,6,9 for 3 total
Number of different outcomes: 10.

Thus the probability is:

Example Question #81 : Probability

A coin is tossed five times. What is the probability of tails occuring at least once?

Possible Answers:

1/2

0.833

0.969

0.729

3/4

Correct answer:

0.969

Explanation:

Probability of getting a head: 0.5
Probability of getting a tail: 0.5


The probability of not getting ANY tails = 0.5 * 0.5 * 0.5 * 0.5 * 0.5= 0.03125

The probability of getting AT LEAST 1 tail = 1 - 0.03125 = 0.969

Example Question #91 : Outcomes

There are 42 candies in a jar.  One-third of the candies are chocolate, one-sixth of the candies are caramel and one-sixth of candies are coconut.  The rest of the candies are mint.  If you select three pieces of candy from the jar, what is the approximate probability that two are chocolate and one is coconut?  

Possible Answers:

5.5%

16.7%

2.2%

1.8%

3.5%

Correct answer:

5.5%

Explanation:

Total Chocolates = 1/3 * 42 = 14

Total Coconuts = 1/6 * 42 = 7

There are 14 chocolates and 7 coconuts to choose from 42 total candies, and note that each time you select one candy, the total number of candies decreases by one. 

So assume that to arrive at the desired outcome of two chocolate and one coconut, you chose two chocolates and then a coconut. After picking out the first chocolate, there are now 13 chocolates to choose from 41 total candies. And after picking out the second chocolate, that leaves 7 coconuts to choose from 40 total candies.

The probability of that outcome = (14/42)(13/41)(7/40) = 0.01849, or just under 1.85%

However, there are two other sequences that could arrive at that desired outcome: chocolate, coconut, chocolate (which would be 14/42 * 7/41 * 13/40 = 1.85%) and coconut, chocolate, chocolate (which would be 7/42 * 14/41 * 13/40 = 1.85%). So summing all three probabilities of favorable outcomes gives you approximately 5.5% 

 

 

Example Question #1 : Trigonometry

Triangle

What is the tangent of C in the given right triangle??

Possible Answers:

Correct answer:

Explanation:

Tangent = Opposite / Adjacent

Example Question #1 : Trigonometry

Consider a right triangle with an inner angle .

If

and

what is ?

Possible Answers:

Correct answer:

Explanation:

The tangent of an angle x is defined as

Substituting the given values for cos x and sin x, we get

Example Question #2 : Trigonometry

Triangle

Triangle ABC shown is a right triangle. If the tangent of angle C is , what is the length of segment BC?

Possible Answers:

Correct answer:

Explanation:

Use the definition of the tangent and plug in the values given:

tangent C = Opposite / Adjacent = AB / BC = 3 / 7

Therefore, BC = 7.

Example Question #4 : Tangent

If the sine of an angle equals , and the cosine of the same angle equals , what is the tangent of the angle?  

Possible Answers:

Correct answer:

Explanation:

The cosine of the angle is  and since that is a reduced fraction, we know the hypotenuse is  and the adjacent side equals .  

The sine of the angle equals , and since the hyptenuse is already  we know that we must multiply the numerator and denominator by  to get the common denominator of .  Therefore, the opposite side equals .  

Since , the answer is

Example Question #1 : How To Find An Angle With Tangent

Soh_cah_toa

For the above triangle,  and . Find .

Possible Answers:

This triangle cannot exist.

Correct answer:

Explanation:

With right triangles, we can use SOH CAH TOA to solve for unknown side lengths and angles. For this problem, we are given the opposite and adjacent sides of the triangle with relation to the angle. With this information, we can use the tangent function to find the angle.

Example Question #1 : Tangent

Soh_cah_toa

In the above triangle,  and . Find .

Possible Answers:

Correct answer:

Explanation:

With right triangles, we can use SOH CAH TOA to solve for unknown side lengths and angles. For this problem, we are given the opposite and adjacent sides of the triangle with relation to the angle. With this information, we can use the tangent function to find the angle.

 

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