Try to guess the number of cubes in the following arrangements (Fig 15.17).
i) There are 4 columns and 2 rows in the first line.
So, the total number of cubes in the first line is
And there is total 3 such line.
Therefore, the total number of cubes are
ii) There are 3 columns and 1 row in the first line at the bottom.
So, the total number of cubes in the first line are
And there are total 2 such lines
So, the total number of cubes at the bottom are
Now, we can see that two cubes are placed on the second line
Therefore, the total number of cubes are
iii) There are 3 columns and 1 row in the first line at the bottom.
So, the total number of cubes in the first line are
And there are total 2 such lines
So, the total number of cubes at the bottom are
Now, we can see that two cubes are placed on the second line and one cube in the front of the first line
Therefore, the total number of cubes are