1. What is the plural of formula?

Both formulas and formulae can be used.

2. When working out the values in an formula does the BEDMAS rule apply?

Yes, the BEDMAS rule for the order that you do operations applies to all mathematics.

3. What is the most common mistakes made by people using a formula?

Often the mistake will be to do with using the wrong types of units or leaving the answer with no units at all.

Frequently, for example, one length will be given in metres and another in centimetres. These must be changed to the SAME units