Theory:

The unitary method is one of the methods to find out the required quantity of value when the value for another quantity is given.

First, the value of one unit will be found. It will be useful to find the value of the required number of units.
Steps to solve the problem using the unitary method.
1. Convert the given problem in mathematical form.
2. Find out the value of one unit of the given item.
3. Find the value of the required number of the item with the help of multiplication.
Example:
Consider the cost of $$4$$ apples is $$₹100$$. Then what will be the cost of $$10$$ apples?

To find this first, we have to determine the cost of one apple (price per unit).

Then we can use this single quantity value to find out the required quantity.

Therefore the cost of $$4$$ apples $$= ₹100$$.

Then the cost of $$1$$ apple $$= ₹$$$\frac{100}{4}$ $$= ₹$$25.

Therefore, the cost of $$1$$ apple $$= ₹$$25.

Cost of $$10$$ Apples $$=$$ Cost of $$1$$ Apple $$\times$$ $$10$$.

That is the cost of $$10$$ apples $$=$$ 25 $$× 10 = ₹$$250.