The 3rd and 7th term of a GP are 24 and 8/27 respectively . Calculate the positive value of the common ratio

Mathematics

ScanSolve AI Answer

Answer

13\frac{1}{3}

Step-by-step solution

4 steps
  1. Write down the formula for the nn-th term of a GP.

    The nn-th term of a Geometric Progression is given by an=a⋅rn−1a_n = a \cdot r^{n-1}, where aa is the first term and rr is the common ratio.

  2. Use the given information to form two equations.

    The 3rd term (a3a_3) is 24:

    a3=a⋅r3−1=a⋅r2=24(1)a_3 = a \cdot r^{3-1} = a \cdot r^2 = 24 \quad (1)

    The 7th term (a7a_7) is 827\frac{8}{27}:

    a7=a⋅r7−1=a⋅r6=827(2)a_7 = a \cdot r^{7-1} = a \cdot r^6 = \frac{8}{27} \quad (2)
  3. Divide equation (2) by equation (1) to eliminate aa.

    a⋅r6a⋅r2=82724\frac{a \cdot r^6}{a \cdot r^2} = \frac{\frac{8}{27}}{24} r6−2=827×24r^{6-2} = \frac{8}{27 \times 24} r4=8648r^4 = \frac{8}{648}
  4. Simplify the fraction and solve for rr.

    r4=181r^4 = \frac{1}{81}

    To find rr, take the fourth root of both sides:

    r=1814r = \sqrt[4]{\frac{1}{81}}

    Since we are asked for the positive value of the common ratio:

    r=14814r = \frac{\sqrt[4]{1}}{\sqrt[4]{81}} r=13r = \frac{1}{3}

    The positive value of the common ratio is 13\frac{1}{3}.

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