Turn 4 1/2 into a fraction which is 4.5, then divide that by three. 4.5 / 3 = 1.5. So 1.5 = 1/3 of the original amount. Now all you need to do is multiply 1.5 times 2. You do this because you know that 1/3 + 1/3 = 2/3. So 1.5 + 1.5 = 2/3. 1.5 * 2 = 3. Now you have 2/3 of the original number.
