We are asked for the approximate average price per bottle, which means that we should look to round off certain values. However, the answers are close together, so we do not want to run the risk of doing too much rounding, otherwise we might select one of the incorrect answers.

To avoid that outcome, we should keep the prices as is and consider the number of bottles purchased.If we were to double the number of small bottles, then we would end up with \(690 \times 2 = 1380\). This is almost exactly the number of large bottles, so we have an approximate ratio of large bottles to small bottles in the ratio of \(2:1\).

With the ratio, the average will be the same regardless of the number of bottles involved, so we can calculate assuming that there are just 2 large bottles and 1 small bottle.

The average price paid per bottle would be

\(Average=\frac{(2×1.89)+(1×1.38)}{2+1}=\frac{5.16}{3}=1.72\)

The final answer is

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