Question

If $9,x,x$ and $49$ are in proportion, find the value of $x$.

• A. $7$
• B. $14$
• C. $21$
• D. $35$

Answer 1

The correct option is C

$21$

Given: $9,x,x,49$ are in proportion i.e. $9:x::x:49$
$\Rightarrow \frac{9}{x}=\frac{x}{49}$

$\Rightarrow x\times x=9\times 49$
$\Rightarrow x\times x=441$
$\Rightarrow x\times x=21\times 21$
$\Rightarrow x=21$