UPSC Prelims 2014 · CSAT

Question 45: Logical Reasoning and Mental Ability

Consider the following figures :

Change in positions of beads in the four figures above follows a sequence. Following the same sequence, which of the figures below should appear as the fifth figure above ?

A row of four square figures with half-black and half-white beads at the corners, followed by a box with a question mark, and below it four option figures (a) to (d) of the same kind. The options are pictures.

aFigure (a)

bFigure (b)

cFigure (c)

dFigure (d)

AnswerUPSC’s answer is (b).

Each of the four beads is a circle that is half black and half white. Across the four figures the black halves change position bead by bead according to a pattern. The fifth figure is the one that continues that pattern from the fourth figure, and UPSC's key gives (b). To check any option, compare each bead's black half in the fourth figure with the option and see whether the same kind of change continues.

Why each option is right or wrong

(a) Does not continue the bead-by-bead sequence.
(b) Right. This is the figure that continues the sequence.
(c) Does not continue the bead-by-bead sequence.
(d) Does not continue the bead-by-bead sequence.

Worth knowing: The printed figures are small, so this explanation follows UPSC's key without a bead-by-bead check of the sequence.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2014, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.