UPSC Prelims 2015 · CSAT
Question 54: Logical Reasoning and Mental Ability
Each of the six different faces of a cube has been coated with a different colour i.e., V, I, B, G, Y and O. Following information is given :
- 1.Colours Y, O and B are on adjacent faces.
- 2.Colours I, G and Y are on adjacent faces.
- 3.Colours B, G and Y are on adjacent faces.
- 4.Colours O, V and B are on adjacent faces.
Which is the colour of the face opposite to the face coloured with O ?
AnswerUPSC’s answer is (c).
On a cube, three faces meeting at a corner are mutually adjacent, so no two of them can be opposite. Y is with O and B, with I and G, and with B and G, so Y touches O, B, I and G; its opposite is V. B is with Y and O, with G and Y, and with O and V, so B touches Y, O, G and V; its opposite is I. The only colours left are O and G, so they are opposite each other. The face opposite O is G.
Why each option is right or wrong
- (a) Wrong: B appears in a corner with O (clues 1 and 4), so it is adjacent.
- (b) Wrong: V is in a corner with O (clue 4), so it is adjacent.
- (c) Right: O and G are the only pair left once Y-V and B-I are paired.
- (d) Wrong: I is opposite B, not O.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2015, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.