Mathematics - Fractions - Adding and subtracting fractions with unlike denominators - Different Size Pieces

Show two fraction bars: 1/2 and 1/3. 'Can you add these directly? They're different sizes!' Show visually that you can't just add 1+1=2 and pick a denominator. You need same-size pieces first. Then show both converted to sixths (3/6 + 2/6 = 5/6). Do 3 similar visual problems. The goal: motivate WHY