Question

In each of the following question, select the related number from the given alternatives.
$5$ $:$ $21$ $:$ $:$ $7$ $:$ $?$

• A. $25$
• B. $49$
• C. $43$
• D. $30$

Answer 1

The correct option is C $43$

In first part $5:21$

$21=5^2-(5-1)$

similarly for second part $7:?$

$?=7^2-(7-1)=43$

therefore option C is correct