HOTS Mathematics Primary 5 Volume

A staircase solid is built from unit cubes. The bottom column has 3 cubes high, the middle column has 2 cubes high, and the right column has 1 cube high (viewed from the front). The solid is 2 unit cubes deep. How many unit cubes are needed to build this solid?

A 12
B 6
C 18
D 9
Show Worked Solution

Worked Solution

Step 1: Count cubes in one layer (1 unit deep), column by column. Left column: 3 cubes high Middle column: 2 cubes high Right column: 1 cube high Total for 1 layer = 3 + 2 + 1 = 6 cubes Step 2: Multiply by depth. 6 × 2 = 12 cubes

Correct answer: 12

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