ACT Math : Matrices

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #2 : How To Find An Answer With A Matrix

Below is a matrix of the items in Jon's wardrobe:

How many combinations of blue pants and red shirts can Jon wear for the upcoming 4th of July party?

Possible Answers:

Correct answer:

Explanation:

If Jon has three red shirts and two blue pants. The total number of combinations of one shirt and one pair of pants he can wear is going to be the number of shirts he can wear with the first pair of pants, , plus the number of shirt he can wear with the second pair of pants, also . That sums to  total outfits.

Example Question #8 : How To Find An Answer With A Matrix

Read the following problem:

The barista at the Teahouse of the December Sun has a problem. He needs to mix twenty pounds of two different kinds of tea together to create a blend called Strawberry Peppermint Delight. The two varieties are Peppermint Nirvana, which costs $12 a pound, and Strawberry Fields, which costs $15 a pound; the new tea will cost $13 a pound, and it will sell for the same price as the two blended teas would separately. How much of each variety will go into the twenty pounds of Strawberry Peppermint Delight?

Which of the following augmented matrices represents the system of equations that could be set up to solve this problem?

Possible Answers:

Correct answer:

Explanation:

If the barista mixes  pounds of Peppermint Nirvana and  pounds of Strawberry Fields to make twenty pounds of tea total, then

will be one of the equations in the system.

 pounds of Peppermint Nirvana tea for $12 a pound will cost a total of  dollars;  pounds of Strawberry Fields tea will cost a total of  dollars. Tewnty pounds of the Strawberry Peppermint Delight tea for $13 a pound will cost  dollars. Since the tea will sell for the same price blended as separate, the other equation of the system will be

The augmented matrix of this system will comprise the coefficients of these equations, both of which are in standard form, so the matrix will be

.

Example Question #1 : Matrices

Simplify:

Possible Answers:

Correct answer:

Explanation:

Matrix addition is very easy! All that you need to do is add each correlative member to each other. Think of it like this:

Now, just simplify:

There is your answer!

Example Question #21 : Matrices

Simplify:

Possible Answers:

Correct answer:

Explanation:

Matrix addition is really easy—don't overthink it! All you need to do is combine the two matrices in a one-to-one manner for each index:

Then, just simplify all of those simple additions and subtractions:

Example Question #1 : How To Add Matrices

What is the value of 

 ?

Possible Answers:

You cannot add these two matrices because their indices do not line up.

Correct answer:

Explanation:

To add matrices you simply add the numbers in the same position as each other.

  

Plugging the given values into the above formula, we are able to solve the question.

   

Example Question #1 : Find The Sum Or Difference Of Two Matrices

Given the following matrices, what is the product of  and ?

 

Possible Answers:

Correct answer:

Explanation:

When subtracting matrices, you want to subtract each corresponding cell.

 

 

Now solve for  and 

 

 

Example Question #2 : Matrices

If , what is ?

 

Possible Answers:

Correct answer:

Explanation:

You can treat matrices just like you treat other members of an equation. Therefore, you can subtract the matrix

from both sides of the equation.  This gives you:

Now, matrix subtraction is simple. You merely subtract each element, matching the correlative spaces with each other:

Then, you simplify:

Therefore, 

Example Question #2581 : Act Math

 

Possible Answers:

 

 

Correct answer:

 

Explanation:

When subtracting matrices, subtracting component-wise.

Example Question #1 : How To Subtract Matrices

If , then what is the value of  ?

Possible Answers:

3

12

15

0

26

Correct answer:

15

Explanation:

 Match each term from the first matrix with the corresponding number from the second matrix and subtract.

Simplify.

 

Each of the numbers in the matrix solution now corresponds to the letters, a through f. Add a (upper left) and (lower right).

Example Question #1 : How To Find Combinations With A Matrix

Matthew, Emily, Cynthia, John, and Stephanie are all running for student council.  If three equivalent positions are available in this year's election, how many different leadership boards are possible?

Possible Answers:

Correct answer:

Explanation:

One possible approach is to enumerate all possibilities using initials for names (ie. MEC, MEJ, MES, etc). If we recognize that order does not matter in this problem, we can also enter  into our calculators, and that will give us the answer of .

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