PSLE John glued 20 cubes of side 1 cm to form the solid shown.
- John painted the whole solid, including the base. What was the total painted area?
- John added some cubes of side 1 cm to the solid to form a cuboid 5 cm by 4 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 + 8 + 8 + 5 + 5
= 58 cm
2 (b)
Number of cubes in the solid = 20
Number of cubes needed to form the cuboid
= 5 x 4 x 4
= 80
Number of cubes that John needed to add
= 80 - 20
= 60
Answer(s): (a) 58 cm
2; (b) 60