How many cubes are there in a group?

The correct answer is Option (4) → 20

The cubes are piled like steps, so every cube that is seen on top rests on a column of hidden cubes below it. Count the cubes column by column, by the height of each column (the step on which its top cube sits):

• Lowest step (the front row along the bottom): 4 columns of 1 cube = 4

• Second step: 3 columns of 2 cubes = 6

• Third step: 2 columns of 3 cubes = 6

• Top step: 1 column of 4 cubes = 4

• Total = 4 + 6 + 6 + 4 = 20

Only 10 cubes (4 + 3 + 2 + 1) can be seen; the other 10 are hidden supports under the upper steps.