Unitary method
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 hence 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.