The unitary method is a technique which is used for solving a problem by finding the value of a single unit, i.e., 1, (by dividing) and then finding the necessary value by multiplying the single unit value. In essence, the unitary method is used to find the value of a unit from the value of a multiple, and thence the value of a multiple .In unitary method it is not always necessary to find the value of single unit let us study it with the help of example
For example, to solve the problem: 'A man walks 7 miles in 2 hours. How far does he walk in 7 hours?', one would first calculate how far the man walks in 1 hour. One can safely assume that he would walk half the distance in half the time. Therefore, dividing by 2, the man walks 3.5 miles in 1 hour. Multiplying by 7 for 7 hours, the man walks 7x3.5=24.5 miles or let us consider the distance travelled by man be X then divide it given distance that is 7 (x/7) it is equal to time take to travel X distance that is 7 hours divided time taken to travel 7 miles that is 2 hours (7/2) therefore x/7=7/2 hence X=24.5 miles.
The same method can be applied to the problem: 'A man walks at 4 miles per hour. How long would it take him to cover 5 miles?'. Dividing by 4 shows that the man covers 1 mile in a quarter (0.25) of an hour. Multiplying by 5 shows that the man therefore takes 1 hour and a quarter (1.25 hours) to cover 5 miles.Similarly by the second method we can find the value of time taken to cover 5 miles. 1st method is more preferable and easier.