Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Numerical Ability

Topic

Ratios

Question:

If b is the mean proportional of a and c, then \((a-b)^{3} : (b-c)^{3}\)= ?

Options:

\(\frac{a^{3}}{b^{3}}\)

\(\frac{a^{2}}{b^{2}}\)

\(\frac{a^{3}}{c^{3}}\)

\(\frac{b^{3}}{a^{3}}\)

Correct Answer:

\(\frac{a^{3}}{b^{3}}\)

Explanation:

b is the mean proportional of a and c

⇒ b² = ac

Now,

\((a-b)^{3} : (b-c)^{3}\)

= \(\frac{ (a - √ac)³ }{(√ac  - c )³}\)

= \(\frac{ [√a (√a - √c)]³ }{[√c (√a - √c)]³}\)

= \(\frac{ [√a]³ }{[√c ]³}\)

= \(\frac{ (√a)3/2 }{[√c ]3/2}\)