Unitary method
Let we see a problem.
If the cost of 3 pens is M12, what will be the cost of 8 pens ?
We have to find the cost of 8 pens, we know that it will be more than the cost of one pen. So we multiply M4 by 8 and we get M32. So the cost of 8 pens is M8 × 4 = M32
In the process of our calculation we found out the value of one unit (in this case cost of one pen)
So this method of solving is called unitary method.
The method in which first we find the value of one unit and then the value of required number of units is known as Unitary Method.
Ex.1     If the cost of 6 cans of juice is M210, then what will be the cost of 4 cans of juice?
Sol.    Cost of 6 cans of juice = M210 Ex.2    A motorbike travels 220 km in 5 litres of petrol. How much distance will it cover in 1.5 litres of petrol?
Sol.    In 5 litres of petrol, motorbike can travel 220 km. Ex.3    If the cost of a dozen soaps is M153.60, what will be the cost of 15 such soaps?
Sol.    We know that 1 dozen = 12
Since, cost of 12 soaps = M153.60 