Exercise 3.2

If y varies directly as $x$ , and $y = 8$ when $x = 2$ , find

(i) y in terms of $x$ (ii) y when $x = 5$ (iii) $x$ when $y = 28$

If $y \propto x$ , and $y = 7$ when $x = 3$ find

(i) y in terms of $x$ (ii) $x$ when $y = 35$ and $y$ when $x = 18$

If $R \propto T$ and $R = 5$ when $T = 8$ , find the equation connecting $R$ and $T$ . Also find $R$ when $T = 64$ and $T$ when $R = 20$ .

If $R \propto T^2$ and $R = 8$ when $T = 3$ , find $R$ when $T = 6$ .

If $V \propto R^3$ and $V = 5$ when $R = 3$ , find $R$ when $V = 625$ .

If $w$ varies directly as $u^3$ and $w = 81$ when $u = 3$ . Find $w$ when $u = 5$ .