Question relating to inverse proportionality.

Question

I just came across a question I can't seem to understand, perhaps it it worded wrong that I do not know. The question is:

$y$ is inversely proportional to $x^3y=44$, when $x=a$. Find $y$ when $x=2a$

Yes, you need to insert “, and” between $x^3$ and $y$, in other words, it should say: “$y$ is inversely proportional to $x^3$, and $y=44$ when $x=a$“... — , Dec 05 '20 at 17:30

score 1 · Accepted Answer · answered Dec 05 '20 at 17:34

1

$$y\propto \dfrac{1}{x^3}$$

means $$y= \dfrac{\text{constant}}{x^3} \quad \text{or,} \quad yx^3 = \text{constant}$$

So $$y \cdot a^3 = y' \cdot (2a)^3 $$ $$\Rightarrow y' = \dfrac{y}{2^3} = \dfrac{44}{8}$$

answered Dec 05 '20 at 17:34

cosmo5

1

Thank you, I was after all using the wrong approach to solve the question. – aayush Dec 05 '20 at 17:44

1 Answers1