All ACT Math Resources
Example Questions
Example Question #21 : How To Find F(X)
For all values of x, f(x) = 7x2 – 3, and for all values of y, g(y) = 2y + 9. What is g(f(x))?
14y2 + 3
7y2 – 3
14x2 – 3
2x + 9
14x2 + 3
14x2 + 3
The inner function f(x) is like our y-value that we plug into g(y).
g(f(x)) = 2(7x2 – 3) + 9 = 14x2 – 6 + 9 = 14x2 + 3.
Example Question #22 : How To Find F(X)
Find
Simply plug 6 into the equation and don't forget the absolute value at the end.
absolute value = 67
Example Question #23 : How To Find F(X)
An outpost has the supplies to last 2 people for 14 days. How many days will the supplies last for 7 people?
Supplies are used at the rate of .
Since the total amount of supplies is the same in either case, .
Solve for days to find that the supplies will last for 4 days.
Example Question #24 : How To Find F(X)
Worker can make a trinket in 4 hours, Worker can make a trinket in 2 hours. When they work together, how long will it take them to make a trinket?
The rates are what needs to be added. Rate is , or one trinket every 4 hours. Rate is , one per two hours.
, their combined rate in trinkets per hour.
Now invert the equation to get back to hours per trinket, which is what the question asks for:
Example Question #25 : How To Find F(X)
Quantity A Quantity B
Quantity B is greater
Quantity A and Quantity B are equal
Quantity A is greater
The relationship cannot be determined from the information given.
Quantity A and Quantity B are equal
Since , then we have that
and
.
Thus, the two quantities are equal.
Example Question #2691 : Act Math
If the average of two numbers is and one of the numbers is , what is the other number, in terms of and ?
The average is the sum of the terms divided by the number of terms. Here you have and the other number which you can call . The average of and is . So
Multiply both sides by 2.
Solve for .
Example Question #1201 : Algebra
Alice is twice as old as Tom, but four years ago, she was three years older than Tom is now. How old is Tom now?
The qustion can be broken into two equations with two unknows, Alice age and Tom's age .
Example Question #26 : How To Find F(X)
A jet goes from City 1 to City 2 at an average speed of 600 miles per hour, and returns along the same path at an average speed if 300 miles per hour. What is the average speed, in miles per hour, for the trip?
450miles/hour
300miles/hour
500miles/hour
350miles/hour
400miles/hour
400miles/hour
Chose a number for the distance between City 1 and 2; 1800 works well, as it is a multiple of 600 and 300.
Now, find the time for each trip, the total distance, and the total time.
Now we can find the average speed by dividing the total distance by the total time.
Example Question #27 : How To Find F(X)
Find .
Plug 5 into first:
Now, plug this answer into :
Example Question #1204 : Algebra
If and , what is ?
Plug g(x) into f(x) as if it is just a variable. This gives f(g(x)) = 3(x2 – 12) + 7.
Distribute the 3: 3x2 – 36 + 7 = 3x2 – 29
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