SSC CHSL 10 Aug 2021 Shift 1 Paper

Section: Quantitative Aptitude

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Question : 74 of 100

Marks: +1, -0

Sunil can row a boat

20 {km}

upstream in

1 {h} {} 15 {min}

. If the speed of the current of the river is

2 {km} \/ {h}

, then how much time will he take to row the boat

30 {km}

downstream?

$1 {h} {} 10 {min}$
$1 {h} {} 45 {min}$
$1 {h} {} 30 {min}$
$1 {h} {} 20 {min}$

Solution:

Let the speed of boat in Still water be

x {km} \/ {h}

.
According to the question,

(x-2) \;\; =\;{20}/{{5}/{4}}=\;{20 × 4}/{5}=16

⇒ \;\; x \;\; =16+2

\;\; =18 {km} \/ {h}

∴

Time taken to row the boat

30 {km}

downstream

\;\; =\;{30}/{18+2}=\;{30}/{20}

\;\; =1.5 {h}

⇒ \;\; x \;\; =1 {h} {} 30 {min}

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