Question 70

There are two numbers $$a^2$$ and 9. Their mean proportion is $$b$$, then $$(a^2 + b^2) : (a^2 - b^2) = ?$$

Solution

Mean proportion of $$a^2$$ and $$9$$ is $$b$$

=> $$\frac{a^2}{b}=\frac{b}{9}$$

=> $$9a^2=b^2$$ -------------(i)

To find = $$(a^2 + b^2) : (a^2 - b^2)$$

= $$\frac{a^2+9a^2}{a^2-9a^2}$$

= $$\frac{10}{8}=5:4$$

=> Ans - (A)

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