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NDA 2026
Exam
NDA
Year
2026
Subject
Mathematics
Chapter
Sequences and Series

NDA 2026 · Mathematics · Sequences and Series

Let p , q and r be three unequal numbers such that p , q and r are...

Let pp, qq and rr be three unequal numbers such that pp, qq and rr are in AP. If (q−p)(q-p), (r−q)(r-q) and pp are in GP, then (p+q):(q+r):(r+p)(p+q):(q+r):(r+p) equals

Options

  1. A1:2:31:2:3
  2. B3:4:53:4:5
  3. C3:5:43:5:4
  4. D1:3:21:3:2

Correct answer

C. 3:5:43:5:4

Step-by-step solution

Since pp, qq, and rr are in AP, let the common difference be dd.

Then q−p=dq - p = d and r−q=dr - q = d.

It is given that (q−p)(q - p), (r−q)(r - q), and pp are in GP.

Substituting the values, we get dd, dd, and pp are in GP.

Therefore, d2=d⋅pd^2 = d \cdot p.

Since pp, qq, and rr are unequal, d≠0d \neq 0.

Thus, p=dp = d.

Now, q=p+d=2dq = p + d = 2d and r=p+2d=3dr = p + 2d = 3d.

We need to find the ratio (p+q):(q+r):(r+p)(p+q) : (q+r) : (r+p).

Substituting the values of pp, qq, and rr in terms of dd:

p+q=d+2d=3dp + q = d + 2d = 3d

q+r=2d+3d=5dq + r = 2d + 3d = 5d

r+p=3d+d=4dr + p = 3d + d = 4d

The required ratio is 3d:5d:4d=3:5:43d : 5d : 4d = 3 : 5 : 4.

Answer: 3:5:43:5:4
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