SSC CHSL 4 Aug 2021 Shift 1 Paper

Section: Quantitative Aptitude

Question : 71 of 100

Marks: +1, -0

One-fifth of a journey is covered at a speed of

30 {km} \/ {h}

, one-fourth of the journey at a speed of

25 {km} \/ {h}

and the rest at

60 {km} \/ {h}

. What is the average speed (in

{km} \/ {h}

, correct to one decimal place) for the whole journey?

Solution:

Let the total distance to cover be

d {km}

=\;{d}/{{d}{\;{5}/{30}+{d}/{25}+{d-{d}/{4}-{d}/{5}}/{60}}}

={1}/{{1}/{150}+\;{1}/{100}+{11}/{1200}}={1}/{{8+12+11}/{1200}}

=\frac{1200}/{31}=38.7 {km} \/ {h}

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