One of the most used equations in physics is the one that states the relationship between speed, distance and time. If you know any two of these three, then you can calculate the third. 

                                                                                                                                                         Here are the three equations, which have been re-arranged for you:

 In these equations s stands for speed, d stands for distance and t stands for time.                         

If you haven’t used a formula before then here’s what you do: you look at it as a set of instructions. First, choose the equation with what you want to calculate on the left hand side. Then, follow the instructions on the other side, substituting the numbers you have in place of the letters which represent them.                                                                                         Here’s a worked example that you can follow through:

Bonkers Betty, the psychopathic Ferrari-driving maniacal tyrant, has broken her speedometer as a result of violent head-banging to excessively loud music. As a physicist, she realises that if she measures her distance and a time she can calculate her speed. She drives 100 metres in 40 seconds, then starts to calculate her speed, gets bored, and then asks you to do it. Calculate her speed.