CSAT Solved Papers/ 2024/Q78

2024 CSAT — Q78

Quant Logical & quantitative reasoning 2.5 marks Medium

If in a certain code, ‘POT’ is written as ATOP and ‘TRAP’ is written as APART, then how is ‘ARENA’ written in that code?

A AARENA
B AANREA
C AANEAR
D AANERA Answer

Worked rationale

Recover the rule from both anchors before encoding the target — one anchor alone is ambiguous.

‘POT’ $\to$ ‘ATOP’. Reverse ‘POT’ to get ‘TOP’, then prepend ‘A’: $A + TOP = ATOP$ ✓
‘TRAP’ $\to$ ‘APART’. Reverse ‘TRAP’ to get ‘PART’, then prepend ‘A’: $A + PART = APART$ ✓

The rule is: reverse the word, then prefix the letter ‘A’.

Apply to ‘ARENA’: reverse ‘ARENA’ $\to$ ‘ANERA’ (read $A,R,E,N,A$ backwards: $A,N,E,R,A$ ), then prepend ‘A’:

A + ANERA = AANERA.

Answer: (d) AANERA.

Why the other options miss

A

solved the wrong question: prepends ‘A’ but forgets to reverse, leaving the original spelling intact after the prefix.
B

an arithmetic slip: reverses but transposes two interior letters (writes $\dots NREA$ instead of $\dots NERA$ ), a careless ordering error in the reversal.
C

an arithmetic slip: reverses the bulk correctly but swaps the last two letters ( $\dots EAR$ vs $\dots ERA$ ), mis-ending the word.

Specialist insight

The decisive step is reading the transformation as two independent operations — a reversal and a fixed prefix — and verifying it on both coded pairs, since ‘POT' $\to$ 'ATOP’ alone could be misread as a cyclic shift. Once ‘TRAP' $\to$ 'APART’ confirms “reverse + prefix A,” the encoding is mechanical; the only risk is mis-reversing ‘ARENA’. Write the target out and reverse letter-by-letter ( $A\,R\,E\,N\,A \Rightarrow A\,N\,E\,R\,A$ ) rather than reversing in your head — every wrong option here is a reversal slip, not a rule error.

The trap, in one line

The cipher is reverse-then-prefix-A: 'ARENA' reverses to 'ANERA', prepend A $=$ AANERA $=(d)$ — confirm the rule on both anchors and reverse the target letter-by-letter to dodge a transposition slip.

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