Question

Let the positive numbers $a, b, c, d$ be in $A.P$. Then
$\frac{1}{abc}, \frac{1}{abd}, \frac{1}{acd}, \frac{1}{bcd}$ are in

• A. $A. P.$
• B. $G. P.$
• C. $A. G. P.$
• D. none of these

Answer 1

Answer: (A)

$a, b, c, d$ are in $A. P$.
Reversing the terms, $d, c, b, a$ are also in $A. P$.
Dividing each term by $a b c d$,
$ \frac{1}{abc}, \frac{1}{abd}, \frac{1}{acd}, \frac{1}{bcd}$ are in $A. P.$