If toffees are bought at the rate of 7 for Rs. 6, at what rate per hundred must they be sold to gain 33%?

Chocolates are bought at a rate of 7 for Rs. 6.

∴ Cost price of one Chocolate = Rs. 6/7.

Let’s assume that the Chocolates are sold at a rate of 100 for Rs. X.

∴ Selling price of one Chocolate = Rs. X/100

According to the information given in the problem, there’s a profit is of 33% in this transaction.

% profit $(= \frac{{selling\;price - cost\;price}}{{cost\;price}} \times 100)$

$(\begin{array}{l} \therefore 33 = \frac{{\left( {\frac{X}{{100}}} \right) - \left( {\frac{6}{7}} \right)}}{{\left( {\frac{6}{7}} \right)}} \times 100\\ \Rightarrow \left( {\frac{{33}}{{100}} \times \frac{6}{7}} \right) + \frac{6}{7} = \frac{X}{{100}}\\ \Rightarrow \frac{{198}}{{700}} + \frac{6}{7} = \frac{X}{{100}}\\ \Rightarrow \frac{{198 + 600}}{{700}} = \frac{X}{{100}}\\ \Rightarrow X = \frac{{798}}{{700}} \times 100 = 114 \end{array})$

∴ Chocolates should be sold at a rate of 100 for Rs. 114.