Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NDA 2018
Exam
NDA
Year
2018
Subject
Mathematics
Chapter
Sequences and Series

NDA 2018 · Mathematics · Sequences and Series

If x, (3)/(2), z are in AP; x, 3, z are in GP; then which one of...

If x,32,zx, \frac{3}{2}, z are in AP; x,3,zx, 3, z are in GP; then which one of the following will be in HP?

Options

  1. Ax, 6, z
  2. Bx, 4, z
  3. Cx, 2, z
  4. Dx, 1, z

Correct answer

A. x, 6, z

Step-by-step solution

x,32,z are  in  A.P \mathrm{x}, \frac{3}{2}, \mathrm{z} \text{\text{ are }\text{ in } A.P }IfIfa, b, care in A.P2b=a+cA.P 2 b=a+c∴2(32)=x+z⇒3=x+z...(1)x,3,z are in G.P. \begin{aligned} & \therefore 2\left(\frac{3}{2}\right)=\mathrm{x}+\mathrm{z} \\ & \Rightarrow 3=\mathrm{x}+\mathrm{z}...(1) \\ & \mathrm{x}, 3, \mathrm{z} \text{ are in G.P. } \end{aligned}If $a, b, c$ are in G.P. $b^2=\mathrm{ac}\begin{aligned} & \therefore 3^2=\mathrm{xz} \\ & \Rightarrow 9=\mathrm{xz}...(2) \end{aligned}$ If $x, 6, z$ are in H.P. $\frac{2}{6}=\frac{1}{x}+\frac{1}{z}\begin{aligned} & \qquad\left(\because \frac{2}{b}=\frac{1}{a}+\frac{1}{c} \text{, if } a, b, c \text{ are is H.P. }\right) \\ & \Rightarrow \frac{1}{3}=\frac{z+x}{x z}=\frac{3}{9}=\frac{1}{3}(\operatorname{from}(1)(2)) \\ & \text{ L.H.S. }=\text{ R.H.S. } \end{aligned}$$$
Practice Sequences and Series on Quantrex Academy →

More from Sequences and Series

Let p , q and r be three unequal numbers such that p , q and r are in AP. If (q-p)… NDA 2026If p^ th term of an AP is k , then what is the sum of p^ th term, (p+q)^ th term and… NDA 2026If p , g_1 , g_2 and q are in GP and m is the arithmetic mean of p and q , then… NDA 2026The sum of the first n terms of an AP is 3n^2+5n . If the m^ th term of the AP is 68… NDA 2026Passage: Let X(a,p) , Y(b,q) and Z(c,r) be the points such that a , b and c are in AP.… NDA 2026If (10 + _ 10 x) , (10 + _ 10 y) and (10 + _ 10 z) are in AP, then consider the following… NDA 2025How many terms of the series 1 + 3 + 5 + 7 + … amount to a sum equal to 12345678987654321… NDA 2025For the following two (02) items: Let (6 + 10 + 14 + … up to m terms) = (1 + 3 + 5 + 7 +… NDA 2025For the following two (02) items: Let (6 + 10 + 14 + … up to m terms) = (1 + 3 + 5 + 7 +… NDA 2025How many terms are identical in the two APs 19, 21, 23, … up to 110 terms and 19, 22, 25… NDA 2025If p , 1 , q are in AP and p , 2 , q are in GP, then which of the following statements… NDA 2025The sum of the first 8 terms of a GP is five times the sum of its first 4 terms. If r ≠ 1… NDA 2025If 5th, 7th and 13th terms of an AP are in GP, then what is the ratio of its first term… NDA 2025The sum of the first k terms of a series S is 3k^2 + 5k . Which one of the following is… NDA 2025What is the harmonic mean of the numbers C(10,3) , C(10,4) , C(10,5) , C(10,6) and… NDA 2025If p times the p^ th term of an AP is equal to q times the q^ th term (p ≠ q) , then what… NDA 2024 Full Sequences and Series list Sequences and Series JEE Maths PYQsJEE Mathematics PYQs All NDA PYQs