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What is the common ratio of a geometric progression if the 6th term is 192 and the second term is 12?

Published in Math Progression 1 min read

The common ratio of the geometric progression is 2.

Here's how to find it:

Understanding Geometric Progressions

A geometric progression is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio. The general formula for the nth term (aₙ) of a geometric progression is:

*aₙ = a r^(n-1)**

Where:

  • a is the first term.
  • r is the common ratio.
  • n is the term number.

Solving for the Common Ratio

We are given:

  • The 6th term (a₆) = 192
  • The 2nd term (a₂) = 12

From the formula above we have:

  • a₂ = ar^(2-1) = ar = 12
  • a₆ = ar^(6-1) = ar^5 = 192

We can express a₆ as a₂ times r⁴:

  • a₆ = a₂ * r⁴
  • 192 = 12 * r⁴

Now we solve for r⁴:

  • r⁴ = 192 / 12
  • r⁴ = 16

Finally, we solve for r:

  • r = ⁴√16
  • r = 2

Therefore, the common ratio (r) is 2, as stated in the reference which says "Thus 192 = 12*r⁴. r⁴ = 16. r=2."

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