Rice vs Wheat

If the cost of wheat is $x$ , then the cost of rice is $1.2x$ . Hence wheat is cheaper by:

$\dfrac{1.2x - x}{1.2x} = \dfrac{\cancel{x} 0.2}{\cancel{x} 1.2} \implies \boxed{16.67 \%}$

Let cost of wheat be $\text{Rs. 100}$ .

So cost of rice $=\text{Rs. 120}$ .

Wheat is cheaper by $\dfrac{(\text{Rs. 120}- \text{Rs. 100})}{\text{Rs. 120}} \times 100\% \approx \boxed{16.67\%}$