Often in science or financial mathematics, we have formulae (which are really equations) consisting of several variables and we know a given value for all of the variables except one of them. To work out the missing value we make the unknown variable the subject of the formula and substitute the other values e.g.:
Distance (D) travelled is speed(s) X time taken (t) [ D=st] so if a car took 2 hours to travel 210 km what was its speed?
D= st ∴ s= D/t = 210/2 ∴ s= 105 km/hr
INEQUALITIES
Sometimes the relationship between two or more quantities is not an exact one but a possible range of values e.g.
John (j) is older than double Mary’s age (m) and he is younger than 18. What is the possible range of Mary’s age?
j > 2m ≤ 17 ∴ 2m ≤16 ∴ m ≤ 8.
Inequalities are solved in the same way as equations but the solution is within a range rather than an exact number.
Tip: Less than points Left <; gReater than points Right >