Did you notice the 4 single dashes on the sides of the cuboid?

This tells you that all 4 sides are equal in length (basically a square)


So the cuboid's height is also 9cm.


This is already given in the question.

Area of remaining solid

= Area of cuboid - area of cube that is cut out

= 9cm × 3cm × 9cm - 3cm × 3cm × 3cm

= 243 cm³ - 27 cm³

= 216 cm³

Another way to think about this question :


The cuboid has dimensions 9cm by 3cm by 9cm.

It could be divided into 9 cubes each 3cm by 3cm by 3cm.


Cutting out 1 cube to form the solid leaves a remaining volume equal to 8 such cubes.


Remaining solid's volume

= 8 × 3 cm × 3 cm × 3 cm
= 8 × 27 cm³
= 216 cm³

Thank you so much !! Thank u J I understand now!!thanks