Q.If \(b\propto a^3\) and \(a\) increases in the ratio \(2:3\), determine the ratio in which \(b\) will increase.

\(\because b\propto a^3\, \, \therefore b=ka^3\) [\(k\) is a nonzero constant]

\(\because a\) increases in the ratio 2:3.
So, let the initial value of \(a\) be \(2m\) and the increased value be \(3m\).

\(\therefore\) Before the increase, \(b=k\cdot (2m)^3 = 8km^3\)
And after the increase, \(b=k\cdot (3m)^3=27km^3\)
\(\therefore\) The ratio of increase in \(b\) is \(\cfrac{8km^3}{27km^3}=8:27\)

\(\therefore\) \(b\) will increase in the ratio 8:27.
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