GED Math Practice Questions: Working with Functions

By Achim K. Krull, Dale E. Shuttleworth, Murray Shukyn

Functions are based on the concept that one number can be determined by its relationship with another number. This is pretty fundamental stuff, so you can expect to see questions involving functions on the GED Math test.

Here’s a simple example of a function: A dozen always consists of 12 units. So, if you were buying two dozen eggs, you’d be buying


In the following practice questions, you have to use a function to find a missing value in a table, and then figure out how energy is affected by a change in mass, based on Einstein’s equation (that is, function) for the speed of light.

Practice questions

The first question refers to the following table.


  1. Herman developed the following function to amuse himself: F = 2a + 3b2 – 2ab. He kept track of his results in this table. Using Herman’s function, what is the value of x?

    A. 53
    B. –82
    C. 88
    D. 30

  2. Consider the equation E = mc2. If the value of m triples and the value of c remains constant, the effect on E would be how many times larger?

    A. 9 times larger
    B. 27 times larger
    C. 3 times larger
    D. the same

Answers and explanations

  1. The correct answer is Choice (D).

    Using Herman’s function, x = 2(3)– 3(4)(4) – 2(3)(4) = 6 + 48 – 24 = 30.

  2. The correct answer is Choice (C).

    This question tests your knowledge of equations by asking you to analyze how a change in one quantity in an exponential equation, E = mc2, results in a change in another quantity. The variation between E and m in this function is linear and direct, which means that whatever happens to m also happens to E. If m is 3 times larger, so is E.