Formulae Substitution and Rearranging Formulae Substituting into Formulae
Formulae Substitution and Rearranging
Formulae
Substituting into Formulae The process of substitution is replacing a variable with a number. Once the variables have been replaced with the numerical values, you then simplify. Example Find the volume of a cuboid, which has length 2 m, width 1 m, and height of 1. 5 m We know that the V = lwh V = 2� 1� 1. 5 V = 3 m 3 Formulae expression Substitute values Final answer (don’t forget units if appropriate)
Changing the subject of a formulae What would happen if you encountered the following scenario? The volume of a cuboid is 2400 cm 3, and you know the length is 20 cm, and the width is 12 cm. What is the height? Writing it out gives us V = lwh 2400 = 20� 12�h What is h? - We could guess? - Or we could rearrange our formula to make the unknown variable (h) to be on the left hand side h = ? ? ? - This is called making ‘h’ the subject of the formula.
Changing the subject of a formulae This means rearranging the formula to put the variable of interest on the left hand side. How do we do this? ? - rewrite the equation to put the variable of interest on the left hand side - we need to now isolate the variable of interest - undo operations by applying the opposite to both sides of the equation Ø Ø Ø To undo addition we must do subtraction To undo subtraction we must do addition To undo multiplication we must do division To undo division we must do multiplication To undo squaring we take the square root To undo a square root we need to square - we apply the same operation to both sides of the equation
Changing the subject of a formulae
Changing the subject of a formulae
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