SSC CHSL 12 Aug 2021 Shift 3 Paper

Section: Quantitative Aptitude

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Question : 59 of 99

Marks: +1, -0

A, B, C

and

D

are four positive numbers such that

A

is

\;{3}/{4}

times of

B, B

is

\;{4}/{5}

times of

C

and

C

is

\;{3}/{8}

times of

D

. If the average of 4 times of

A

and 7 times of

D

is 316 , then the average of all the four numbers

A, B, C

and

D

is

36
38
28
34

Solution:

Given,

A=\;{3}/{4}

of

B

\;\;\; B=\;{4}/{5} \;\text " of "\; C

\;\text " and "\; \;\; C=\;{3}/{8} \;\text " of "\; D

∴ \;\; A=\;{3}/{4} \;\text " of "\; \;{4}/{5} \;\text " of "\; \;{3}/{8} \;\text " of "\; D

\;\;\; A=\;{9}/{40} \;\text " of "\; D

. . . (i)

\;\text " Given, "\; \;{4 A+7 D}/{2}=316

∴

4 A+7 D=316 × 2=632

⇒ 4 × \;{9}/{40} × D+7 D=316 × 2=632

[ ∵

from Eq. (i)

]

⇒ \;\; D=\;{6320}/{79}=80

∴ \;\; C=\;{3}/{8} × 80=30

,

B=\;{4}/{5}

of

30=24

and

\;\; A=\;{3}/{4} × 24=18

∴

Average of

A, B, C

and

D

=\;{18+24+30+80}/{4}

=\;{152}/{4}=38

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