PSLE Oscar glued 24 cubes of side 1 cm to form the solid shown.
- Oscar painted the whole solid, including the base. What was the total painted area?
- Oscar added some cubes of side 1 cm to the solid to form a cuboid 5 cm by 3 cm by 4 cm. How many cubes did he add?
(a)
Area of one face
= 1 x 1
= 1 cm
2 Total painted area
= 16 + 16 + 12 + 12 + 6 + 6
= 68 cm
2 (b)
Number of cubes in the solid = 24
Number of cubes needed to form the cuboid
= 5 x 3 x 4
= 60
Number of cubes that Oscar needed to add
= 60 - 24
= 36
Answer(s): (a) 68 cm
2; (b) 36