If x: y=3: 1, then x³-y³: x³+y³= ? · ABC26GN3008
Subject: General Aptitude · Chapter: Ratio and Proportion
If $x: y=3: 1$, then $x^{3}-y^{3}: x^{3}+y^{3}=$ ?
(a)10 : 11
(b)11 : 10
(c)13 : 14
(d)14 : 13
Answer
Explanation
$$\begin{aligned} & \frac{x}{y}=\frac{3}{1} \Rightarrow \frac{x^{3}}{y^{3}}=\frac{27}{1} \Rightarrow \frac{x^{3}-y^{3}}{x^{3}+y^{3}}=\frac{\left(\frac{x^{3}}{y^{3}}\right)-1}{\left(\frac{x^{3}}{y^{3}}\right)+1}=\frac{27-1}{27+1}=\frac{26}{28}=\frac{13}{14} \\ & \Rightarrow\left(x^{3}-y^{3}\right):\left(x^{3}+y^{3}\right)=13: 14 . \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.
Study loop for Ratio and Proportion
· Browse this chapter in the app