Try to guess the number of cubes in the following arrangements (Fig 15.17).

          

Answers (1)
G Gautam harsolia

i) There are 4 columns and 2 rows in the first line.
So, the total  number of cubes in the first line is 
 \Rightarrow 4 \times 2 = 8
And there is total 3 such line.
Therefore, the total number of cubes are \Rightarrow 8\times 3 = 24

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
\Rightarrow 3 \times 1 = 3
And there are total 2 such lines 
So, the total number of cubes at the bottom are \Rightarrow 3 \times 2 = 6
Now, we can see that two cubes are placed on the second line 
Therefore, the total number of cubes are \Rightarrow 6+2=8

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
\Rightarrow 3 \times 1 = 3
And there are total 2 such lines 
So, the total number of cubes at the bottom are \Rightarrow 3 \times 2 = 6
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 \Rightarrow 6+3=9

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