The problem states that 1/3 of the counters in a bag are red, and the rest are blue. We need to determine the ratio of red to blue counters.

Step-by-step solution:

1. Fraction of red counters: The problem tells us that 1/3 of the counters are red.

2. Fraction of blue counters: Since the rest of the counters are blue, the fraction of blue counters will be: $1 - \frac{1}{3} = \frac{2}{3}$

3. Ratio of red to blue: The ratio of red counters to blue counters is the fraction of red to the fraction of blue, which can be written as: $\text{Ratio of red to blue} = \frac{\frac{1}{3}}{\frac{2}{3}} = \frac{1}{2}$

Thus, the ratio of red to blue counters is 1:2.

Would you like more details, or do you have any questions?

Here are 5 related questions you can explore:

1. If there are 90 counters in total, how many red and blue counters are there?
2. If half of the counters are replaced with red counters, what will the new ratio of red to blue be?
3. What is the percentage of blue counters in the bag?
4. If 2/5 of the counters were red instead, what would the new ratio of red to blue counters be?
5. How would the ratio change if an additional 10 red counters were added?

Tip: To find the ratio between two parts, divide their corresponding fractions or amounts directly.