First find the total flour, then subtract the amount used.<br><br>
&bull; Total flour: 2 &times; 2 = 4 kg<br>
&bull; Convert to tenths: 4 = \(\frac{40}{10}\)<br>
&bull; Left: \(\frac{40}{10} - \frac{9}{10} = \frac{31}{10}\)<br>
&bull; Convert to a mixed number: \(\frac{31}{10} = 3\frac{1}{10}\)<br>
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Final Answer: B: \(3\frac{1}{10}\) kg