ACT Math : Algebra

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #21 : How To Evaluate Algebraic Expressions

If \(\displaystyle E=(F)(G)\), then which of the following is an expression for \(\displaystyle G\) in terms of \(\displaystyle E\) and \(\displaystyle F\)?

Possible Answers:

\(\displaystyle \frac{E}{F}\)

\(\displaystyle (E)(F)\)

\(\displaystyle F-E\)

\(\displaystyle \frac{F}{E}\)

\(\displaystyle E-F\)

Correct answer:

\(\displaystyle \frac{E}{F}\)

Explanation:

Divide both sides by \(\displaystyle F\), giving you

\(\displaystyle G=\frac{E}{F}\).

Example Question #22 : Evaluating Expressions

Find the value of  \(\displaystyle y\) where:

\(\displaystyle 2y+4=3y-2\)

 

Possible Answers:

\(\displaystyle -6\)

\(\displaystyle -\frac{1}{2}\)

\(\displaystyle 0\)

\(\displaystyle \frac{1}{2}\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 6\)

Explanation:

This problem requires utilization of the opposite operations to both sides principle.

 \(\displaystyle 2y+4=3y-2\)

 

Adding +2 to both sides yields

 \(\displaystyle 2y+6=3y\)

 

Subtracting 2y from both sides yields

 \(\displaystyle 6=3y-2y=y\)

 

Example Question #51 : Expressions

Sally is ordering snacks for her class trip. She needs 85 cookies. The cookies come in cases of 6 boxes, with 7 cookies in each box. Sally can't order a partial box. What is the smallest number of cases she should order? 

Possible Answers:

6

4

3

2

1

Correct answer:

3

Explanation:

We first determine how many cookies are in each box. There are 7 cookies in a box, multiplied by 6 boxes, making 42 cookies in a case. We then divide the total number of cookies she needs, 85, by the number in each case, 42, giving us 2 with a remainder. This means Sally must order 3 cases of cookies.

Example Question #52 : Expressions

A company rents cars for a rental fee of $37.00 per day, with an additional charge of $0.45 per mile driven. Which of the following expressions represents the cost, in dollars, of renting the car for 2 days and driving it m miles?

Possible Answers:

0.45m + 74

0.45m + 37

37m + 0.45

74m + 45

37m + 45

Correct answer:

0.45m + 74

Explanation:

To determine cost we add the initial rental fee of $37, times two days giving us $74 plus the mileage rate, 0.45,  times the number of miles. Giving an equation of 0.45m+74.

Example Question #961 : Algebra

If \(\displaystyle x+y=5\), what is the value of:

\(\displaystyle 6(x+y)-(x+y)^2+\frac{1}{5}(x+y)+8\)

Possible Answers:

\(\displaystyle 8\)

\(\displaystyle -6\)

\(\displaystyle 0\)

\(\displaystyle 14\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 14\)

Explanation:

Substituting x+y for 5, we get

6(5) - 5+ (1/5)(5) + 8

30 - 25 + 1 + 8

= 14

Example Question #27 : How To Evaluate Algebraic Expressions

A batting average is determined by calculating the amount of hits a batter accumulates in the amount of at-bats that they have had in a season.  However when a batter walks the at-bat is not counted in the calculation of the batter's batting average.  Walks also have no effect on a batter's hit count.

Let:

Total at-bats, including times a batter has walked = a

Number of hits = b

Number of walks = c

What is an appropriate expression for the calculation of a hitter's batting average?

Possible Answers:

\(\displaystyle \frac{ba}{c}\)

\(\displaystyle \frac{b-c}{a-c}\)

\(\displaystyle \frac{b-c}{a}\)

\(\displaystyle \frac{b}{a-c}\)

\(\displaystyle \frac{b}{a}-c\)

Correct answer:

\(\displaystyle \frac{b}{a-c}\)

Explanation:

To conform to the way in which a batting average is calculated the equation must be set up so that the amount of hits a batter has accumulated is divided by the amount of at-bats the batter has had, without including at-bats that have resulted in a walk. So the equation should be (hits)/((at-bats) – (walks)), this is acheved by b/(a – c).

Example Question #28 : How To Evaluate Algebraic Expressions

If st – 4r = 8, what is the value of t in terms of r and s?

Possible Answers:

(4r + 8)/s

(8 – 4r)/s

(8 – 4s)/r

s(4r + 8)

(4s + 8)/r

Correct answer:

(4r + 8)/s

Explanation:

We rearrange the equation st – 4r=8 by adding 4r to the right side; then divide by s → t = (4r + 8)/s

Example Question #962 : Algebra

Which of the following is equal (10 – 6) if x = 10?

Possible Answers:

(x – 8)(x – 2)

(x + 6)(x – 4)

(x + 4)(x – 4)

(x + 6)(x – 6)

(x + 8)(x + 2)

Correct answer:

(x – 8)(x – 2)

Explanation:

First, you set up and solve the original equation. Set up (10 – 6)2, then solve it, giving you 16. We can then plug in 10 for x in the answer choices until you find the choice that always gives you 16, which is (x – 8)(x – 2).

Example Question #963 : Algebra

If  4x+6y=8\(\displaystyle 4x+6y=8\) , then what is the value of  3(2x + 3y)\(\displaystyle 3(2x + 3y)\) ?

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 24\)

\(\displaystyle 15\)

\(\displaystyle 8\)

\(\displaystyle 10\)

Correct answer:

\(\displaystyle 12\)

Explanation:

The value of  3(2x + 3y)\(\displaystyle 3(2x + 3y)\) is \(\displaystyle 12\)

Note that  2x + 3y = \frac{1}{2}(4x + 6y)\(\displaystyle 2x + 3y = \frac{1}{2}(4x + 6y)\) , so  2x + 3y\(\displaystyle 2x + 3y\)  must equal  \frac{1}{2}(8)\(\displaystyle \frac{1}{2}(8)\) , which is \(\displaystyle 4\) 

Since  2x + 3y = 4\(\displaystyle 2x + 3y = 4\), we can see that  3(2x + 3y) = 12\(\displaystyle 3(2x + 3y) = 12\)

Example Question #964 : Algebra

If \(\displaystyle x\ \blacklozenge \ y\) is defined by the formula \(\displaystyle (x^{3}-y)^{2}-x\), what is \(\displaystyle 2\ \blacklozenge \ 1\) equivalent to?

Possible Answers:

\(\displaystyle 47\)

\(\displaystyle 0\)

\(\displaystyle -1\)

\(\displaystyle 34\)

\(\displaystyle 49\)

Correct answer:

\(\displaystyle 47\)

Explanation:

The function \(\displaystyle x\ \blacklozenge \ y\) is defined by \(\displaystyle (x^{3}-y)^{2}-x\). This means that for whatever value is in the space of the \(\displaystyle x\) before the symbol \(\displaystyle \blacklozenge\), in our case 2, is inserted into any \(\displaystyle x\) in the defined function:

\(\displaystyle \dpi{100} (2^{3}-y)^{2}-2\)

For the value that follows \(\displaystyle \blacklozenge\), the \(\displaystyle y\) value of 1 in our case, is inserted into any \(\displaystyle y\) variable in the defined function.

\(\displaystyle \dpi{100} (2^{3}-1)^{2}-2\)

Then simplify:

\(\displaystyle (8-1)^{2}-2\)

\(\displaystyle 7^{2}-2\)

\(\displaystyle 49-2\)

\(\displaystyle 47\)

\(\displaystyle 47\) is our correct answer after all the simplification.

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