Q151 / 270 · NDA 2026 (Phase 1) · Mathematics
Let $p$, $q$ and $r$ be three unequal numbers such that $p$, $q$ and $r$ are in AP. If $(q-p)$, $(r-q)$ and $p$ are in GP, then $(p+q):(q+r):(r+p)$ equals
- A$1:2:3$
- B$3:4:5$
- Correct answerC$3:5:4$
- D$1:3:2$
Solution
Since $p$, $q$, and $r$ are in AP, let the common difference be $d$.
Then $q - p = d$ and $r - q = d$.
It is given that $(q - p)$, $(r - q)$, and $p$ are in GP.
Substituting the values, we get $d$, $d$, and $p$ are in GP.
Therefore, $d^2 = d \cdot p$.
Since $p$, $q$, and $r$ are unequal, $d \neq 0$.
Thus, $p = d$.
Now, $q = p + d = 2d$ and $r = p + 2d = 3d$.
We need to find the ratio $(p+q) : (q+r) : (r+p)$.
Substituting the values of $p$, $q$, and $r$ in terms of $d$:
$p + q = d + 2d = 3d$
$q + r = 2d + 3d = 5d$
$r + p = 3d + d = 4d$
The required ratio is $3d : 5d : 4d = 3 : 5 : 4$.
Answer: $3:5:4$
Then $q - p = d$ and $r - q = d$.
It is given that $(q - p)$, $(r - q)$, and $p$ are in GP.
Substituting the values, we get $d$, $d$, and $p$ are in GP.
Therefore, $d^2 = d \cdot p$.
Since $p$, $q$, and $r$ are unequal, $d \neq 0$.
Thus, $p = d$.
Now, $q = p + d = 2d$ and $r = p + 2d = 3d$.
We need to find the ratio $(p+q) : (q+r) : (r+p)$.
Substituting the values of $p$, $q$, and $r$ in terms of $d$:
$p + q = d + 2d = 3d$
$q + r = 2d + 3d = 5d$
$r + p = 3d + d = 4d$
The required ratio is $3d : 5d : 4d = 3 : 5 : 4$.
Answer: $3:5:4$
Hence, the correct answer is option: 'C'.