PSAT Math : Algebraic Fractions

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #1 : How To Find Inverse Variation

Find the inverse of .

Possible Answers:

Correct answer:

Explanation:

To find the inverse of a function we need to first switch the  and . Therefore,  becomes

We now solve for y by subtracting 1 from each side

From here we divide both sides by 2 which results in

Example Question #7 : How To Find Inverse Variation

Find the inverse of .

Possible Answers:

Correct answer:

Explanation:

To find the inverse we first switch the variables then solve for y.

Then we subtract  from each side

Now we divide by  to get our final answer. When we divide  by  we are left with . When we divide  by  we are left with . Thus resulting in:

Example Question #1 : How To Find Inverse Variation

Find the inverse equation of:

 

Possible Answers:

Correct answer:

Explanation:

To solve for an inverse, we switch x and y and solve for y. Doing so yields:

 

 

Example Question #1 : How To Find Inverse Variation

Find the inverse equation of  .

Possible Answers:

Correct answer:

Explanation:

1. Switch the  and  variables in the above equation.

 

2. Solve for :

 

Example Question #3 : How To Find Inverse Variation

When ,  .

When .

If  varies inversely with , what is the value of  when ?

Possible Answers:

Correct answer:

Explanation:

If  varies inversely with .

 

1. Using any of the two  combinations given, solve for :

Using :

 

2. Use your new equation  and solve when :

 

Example Question #1 : How To Find Inverse Variation

x

y

If  varies inversely with , what is the value of ?

Possible Answers:

Correct answer:

Explanation:

An inverse variation is a function in the form:  or , where  is not equal to 0. 

Substitute each  in .

Therefore, the constant of variation, , must equal 24. If  varies inversely as must equal 24. Solve for .

Example Question #1 : How To Evaluate A Fraction

Evaluate the following equation when  and round your answer to the nearest hundredth.

Possible Answers:

Correct answer:

Explanation:

 

1. Plug in  wherever there is an  in the above equation.

2. Perform the above operations.

Example Question #1 : How To Evaluate A Fraction

Mary walked to school at an average speed of 2 miles per hour and jogged back along the same route at an average speed of 6 miles per hour. If her total traveling time was 1 hour, what was the total number of miles in the round trip?

Possible Answers:

Correct answer:

Explanation:

Since Mary traveled 3 times as quickly coming from school as she did going to school (6 miles per hour compared to 2 miles per hour), we know that Mary spent only a third of the time coming from school as she did going. If x represents the number of hours it took to get to school, then x/3 represents the number of hours it took her to return.

Knowing that the total trip took 1 hour, we have:

x/3 = 1

3x/3 + 1x/3 = 1

4x/3 = 1

 = 3/4

So we know it took Mary 3/4 of an hour to travel to school (and the remaining 1/4 of an hour to get back).

Remembering that distance =  rate * time, the distance Mary traveled on her way to school was (2 miles per hour) * (3/4 of an hour) = 3/2 miles. Furthermore, since she took the same route coming back, she must have traveled 3/2 of a mile to return as well.

Therefore, the the total number of miles in Mary's round trip is 3/2 miles + 3/2 miles = 6/2 miles = 3 miles.

Example Question #2 : How To Evaluate A Fraction

If w=\frac{1}{8} then which of the following is equal to ?

Possible Answers:

\frac{1}{4}

\frac{1}{64}

\frac{1}{16}

\frac{1}{32}

\frac{1}{2}

Correct answer:

\frac{1}{4}

Explanation:

To raise \frac{1}{8} to the exponent \frac{2}{3}, square \frac{1}{8} and then take the cube root.

Example Question #1 : How To Evaluate A Fraction

Solve   Actmath_7_113_q10_1

 

Possible Answers:

0

no solution

–1

infinitely many solutions

Correct answer:

infinitely many solutions

Explanation:

The common denominator of the left side is x(x–1). Multiplying the top and bottom of 1/x by (x–1) yields

Actmath_7_113_q10_2

Actmath_7_113_q10_3

Actmath_7_113_q10_4

Actmath_7_113_q10_5

 

Since this statement is true, there are infinitely many solutions. 

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