Perform an activity by using a graph paper.
For Instance let us consider a rectangle on a graph sheet, perfectly situating on the both x axis and y axis.
Now, count the number of boxes it covers, that is called as area.
This number is same as the multiplication of the x axis and y axis of the rectangle.
A= X*Y
For this we can use an activiti using a 2 by 5 grid and it be a rectangle
use 1 by 1 square and start placing them on the grid
when the grid is filled properly then count the number of square in the grid=10
then multiply the length and bredth =10
since L*B=10 and area of grid is also = 10 
therefore L*B= area of grid

Hence verified 

hope this helps you 
With Reguards
Vishwas Choudhary