Subtract the amount used from the amount she had by converting to a common denominator.<br><br>
&bull; \(3\frac{2}{5} = \frac{17}{5}\) and \(1\frac{1}{4} = \frac{5}{4}\)<br>
&bull; LCM of 5 and 4 is 20.<br>
&bull; \(\frac{17}{5} = \frac{68}{20}\) and \(\frac{5}{4} = \frac{25}{20}\)<br>
&bull; \(\frac{68}{20} - \frac{25}{20} = \frac{43}{20}\)<br>
&bull; Convert to mixed number: \(\frac{43}{20} = 2\frac{3}{20}\)<br><br>
Helen had \(2\frac{3}{20}\) kg of rice left.<br>
Check: \(2\frac{3}{20} + 1\frac{1}{4} = 2\frac{3}{20} + 1\frac{5}{20} = 3\frac{8}{20} = 3\frac{2}{5}\). ✓