**1. Is there a quick way to work out how much an item costs after GST at 15% has been added on?**

Yes, multiply by 9 and divide by 8. (In other words multiply by

(100 + 15)/100which simplifies to23/20).

**2. When multiplying mixed numbers should they be changed to improper fractions?**

Yes, it is almost always easier to do this first and then to cancel.

**3. When working out percentage profit and loss problems is the ORIGINAL amount always used?**

Yes. This applies to working out discount percentages too.