Addition of fractions

Mr Creamer
1. Choose your fractions by inputting numbers into the four boxes. Each fraction should be less than 1 2. The fractions are represented by partly filled boxes below 3. Drag the Add slider to push the boxes together. Can you count the boxes to work out the fraction sum? Do you know what the LCM (Lowest common denominator) of the two denominators (bottom halves) are? 4. Select the LCM check box. Drag the Add slider again - can you work out the fraction sum now?