PSLE Ben glued 18 cubes of side 1 cm to form the solid shown.
- Ben painted the whole solid, including the base. What was the total painted area?
- Ben added some cubes of side 1 cm to the solid to form a cuboid 3 cm by 4 cm by 3 cm. How many cubes did he add?
(a)
Area of one face
= 1 x 1
= 1 cm
2 Total painted area
= 9 + 9 + 16 + 16 + 6 + 6
= 62 cm
2 (b)
Number of cubes in the solid = 18
Number of cubes needed to form the cuboid
= 3 x 4 x 3
= 36
Number of cubes that Ben needed to add
= 36 - 18
= 18
Answer(s): (a) 62 cm
2; (b) 18