Question

Find the fourth proportional to : 3, 42 and 7

• A. $98$
• B. $84$
• C. $78$
• D. $28$

Answer 1

The correct option is A $98$

In $a:b::c:d;d$ is the fourth proportional.
For, $3:42::7:d$, product of extremes $=$ product of means
$3\times d=42\times 7$
$d=98$