Two types of rice rates are $\text{₹ }11/\text{kg}$ and $\text{₹ }21/\text{kg}$. Find the ratio of the two types of rice to obtain a mixture of rate $\text{₹ }17/\text{kg}$.

Using the rule of alligation:
* Cost of Type 1 rice ($C_1$) = $\text{₹ }11$
* Cost of Type 2 rice ($C_2$) = $\text{₹ }21$
* Mean price ($M$) = $\text{₹ }17$

According to Alligation formula:

$$\frac{\text{Quantity of Type 1}}{\text{Quantity of Type 2}}=\frac{C_2-M}{M-C_1}$$

Substituting the values:

$$\frac{\text{Quantity of Type 1}}{\text{Quantity of Type 2}}=\frac{21-17}{17-11}=\frac{4}{6}=\frac{2}{3}$$

Therefore, the required ratio is $2:3$.