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Q56·CSAT · Prelims 2024

Evaluating divisibility rules across different bases

NumericalDivisibility RulesStatement-basedHard

Question

A person walks 100 m straight from his house, turns left and walks 100 m, again turns left and walks 300 m, then turns right and walks 100 m to reach his office. In which direction does he walk initially from his house if his office is exactly in the North-East direction?

Options

a

North-West

b

West

Answer
c

South

d

South-West

Explanation

Assume an initial direction of North to map the relative layout of the path segments:

1Walk 100 m North.
2Turn left \rightarrow Walk 100 m West.
3Turn left \rightarrow Walk 300 m South (passing original latitude line by 200 m).
4Turn right \rightarrow Walk 100 m West.

Relative displacement map from start point (0,0): Net West = 100 + 100 = 200 m. Net South = 300 - 100 = 200 m. Under a North baseline, the destination points to South-West.

The question specifies the destination must be North-East. To transform a South-West outcome into a North-East outcome, the entire orientation map must be rotated by 180^\circ. Rotating our initial baseline of North by 180^\circ forces the true starting direction to be South.

Self-Correction Check: Let's re-verify rotation. North maps to South-West. We want North-East. Distance is same in magnitude. South-West is exactly opposite to North-East. So rotating by 180 degrees changes North to South. Let's test starting South: 100 South, Left \rightarrow 100 East, Left \rightarrow 300 North, Right \rightarrow 100 East. Net = 200 North, 200 East \rightarrow North-East. Perfect.

For tracking complex pathways with unknown headings, start with a placeholder axis (like North), find the relative endpoint vector, and rotate your axis to match the final absolute compass target.

Answer: (c).

Question details

Year

2024

Paper

CSAT

Question

Q56

Section

Numerical Ability

Sub-topic

Divisibility Rules

Type

Statement-based

Difficulty

Hard

Source hint

Number theory properties

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