What are the first four terms of a geometric sequence if its common ratio is 5 and its first term is 2.5? 2.5, 7.5, 12.5, 17.5
2.5, 0.5, 0.1, 0.02
2.5, 12.5, 62.5, 312.5
2.5, -2.5, -7.5, -12.5

 C:  2.5, 12.5, 62.5, 312.5

Step-by-step explanation:

Let us remember that in a geometric sequence:

    ratio =

We know that (first term) is 2.5.  So plug in the numbers into the above formula:

    5 =

Multiply both sides by 2.5 to solve for (second term):

    5 × 2.5 = 12.5

By process of elimination, it is obvious the correct answer is C.

We can double check your answer by checking the rate is 5 by dividing:

   For example, 62.5 () divided by 12.5 () is appropriately 5.  

   Similarly, 312.5 () divided by 32.5 () is again 5, confirming our answer to be correct.

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