wiz-icon
MyQuestionIcon
MyQuestionIcon
14
You visited us 14 times! Enjoying our articles? Unlock Full Access!
Question

How many smaller cubes have none of their faces coloured?

A
0
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
1
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
2
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
D
4
No worries! We‘ve got your back. Try BYJU‘S free classes today!
E
None of these
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

The correct option is B 2
Two cubes are joined together and painted red. Thereafter, one cube is cut into 8 smaller cubes and the other into 27 smaller cubes. The smaller cubes that are at the corners are painted on three of their faces, and there are 8 such cubes.
Since the two cubes are joined face-to-face before painting, one face of each original cube. remains uncoloured. The cube which is cut into 8 equal smaller cubes has 4 smaller cubes painted on two of their faces. The cube which is cut. into 27 equal smaller cubes has (n2)×8, i.e., 1×8=8 smaller cubes painted on two of their faces. Further, the cube which is cut into 27 smaller cubes has 4 smaller corner cubes painted red on two of their faces. Thus, there are 4 + 8 + 4 = 16 such cubes which are painted red only on two of their faces.
In respect to the cube which is cut into 27 smaller cubes, there are 2 smaller cubes on the inner side which are not painted red. Thus, the total number of cubes that have at least one of their faces painted red is 27 + 8 - 2 = 33. Out of these 33 smaller cubes, 16 cubes are coloured on two faces and 8 cubes are coloured on three faces. So, the remaining 9 cubes are coloured only on one face.

flag
Suggest Corrections
thumbs-up
0
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Energy From the Sea
MATHEMATICS
Watch in App
Join BYJU'S Learning Program
CrossIcon