Theory:

In the previous lesson we learn to perform the addition using the grid models. Now let us take a look how to perform a subtraction using a grid models.
Example:
Find \(0.55 – 0.15\).
 
Here, \(0.65\) can be written as 55100, and \(0.15\) can be written as 15100.
  • In the grid model first shade the region of \(0.55\) and cross out the regions \(0.15\), which means we are excluding \(0.15\) from the total shaded area.
  • The left out shaded regions without the cross marks are the difference between \(0.55\) and \(0.15\).
  • Therefore, the difference is \(0.55 – 0.15 = 0.40\)
7.png
 
Now let's see word problems to understand this concept clearly.
Example:
Riya's mother gave her \(₹ 5.50\) and she used this money to buy a pen. If the shopkeeper gave her \(₹ 1\) what was the pen's rate?
 
To find the pen's rate, subtract the total amount \(₹ 5.50\) with the returned amount \(₹ 1\).
 
8.png
 
That is, \(₹(5.50 – 1) = ₹ 4.50\). Therefore the cost of the pen is \(₹ 4.50\).
In the upcoming exercises we practice to solve more problems in this concept.