If 15 toys cost Rs. 234, what do 35 toys cost ?

More toys, more cost

$\Rightarrow$ Direct proportion using

$\frac{a_1}{b_1}=\frac{a_2}{b_2}$

$\Rightarrow \frac{15}{234}=\frac{35}{x}$

$\Rightarrow 15\times x=35\times 234$

$\Rightarrow x=\frac{35\times 234}{15}=546$

$=$ Rs.546