The selling price (SP) is Rs. 68.20, and the cost price (CP) is calculated using the given profit percentage:
\(\text{Profit} = 10\% \implies SP = 1.1 \cdot CP\).
Substitute SP:
\(68.20 = 1.1 \cdot CP \implies CP = \frac{68.20}{1.1} = Rs. 62.\)
Using the rule of alligation, the ratio in which the two varieties must be mixed is given by:
\(\text{Ratio} = \frac{\text{Difference between higher price and mean price}}{\text{Difference between mean price and lower price}}.\)
Substitute values:
\(\text{Ratio} = \frac{65 - 62}{62 - 60} = \frac{3}{2}.\)
Thus, the grocer must mix the two varieties in the ratio 3 : 2.