Question

Find fourth proportional to 6, 8 and 9?

Answer 1

Solution:

Let a be the required fourth proportional. 

Then 6:8 :: 9:a

or \( \frac{6}{8}=\frac{9}{a} \)

\( ⇒ 6a=8 \times 9 \)

\( ⇒ 6a=72 \)

\( ⇒ a=\frac{72}{6}=12 \)

Thus, the required fourth proportional is 12.

The required fourth proportional is 12.