CSAT Solved Papers/ 2022/Q26

2022 CSAT — Q26

Quant Arithmetic & numeracy 2.5 marks Medium

On one side of a $1.01$ km long road, $101$ plants are planted at equal distance from each other. What is the total distance between $5$ consecutive plants?

A 40 m
B 40.4 m Answer
C 50 m
D 50.5 m

Worked rationale

$101$ plants leave $101 - 1 = 100$ equal gaps along the road. With $1.01$ km $= 1010$ m:

\text{gap} = \frac{1010}{100} = 10.1 \text{ m}.

” $5$ consecutive plants” span $5 - 1 = 4$ gaps:

4 \times 10.1 = 40.4 \text{ m}.

Answer: (b) 40.4 m.

Why the other options miss

A

a convention slip: uses a round gap of $10$ m (treats $1.01$ km as $1$ km), dropping the $0.4$ .
C

off by one: takes $5$ gaps for $5$ plants instead of $4$ , using a $10$ -m gap.
D

off by one: counts $5$ gaps ( $5 \times 10.1$ ), the fencepost miscount on the consecutive plants.

Specialist insight

Two fencepost moments: $101$ plants give $100$ gaps (not $101$ ), and $5$ consecutive plants give $4$ gaps (not $5$ ). The exact arithmetic $1010/100 = 10.1$ also matters — the round answers $40$ and $50$ are bait for anyone who rounds $1.01$ km to $1$ km. Keep both the gap count and the metre value precise.

The trap, in one line

$100$ gaps over $1010$ m $\Rightarrow 10.1$ m each; $4$ gaps span $5$ plants $\Rightarrow 40.4$ m $=$ (b).

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