How many right angles are there at all the corners of a cube?

Q. 18. A cube is painted red on all faces and divided into 27 smaller cubes of equal size. Now a small cube from each corner is removed . How many cubes are there which have none of their face coloured?

Q. Mark against the correct answer
How many 8-digit numbers are there?
(a) 99999999
(b) 89999999
(c) 90000000
(d) none of these

Q.

How many perfect cubes are there from 1 to 500? How many are perfect squares among these cubes?

Q. How many right angles are present at all corners of a cube?