RRB RPF RPSF SI and CONS Model Papers 3 with solutions

Question : 26 of 120

Marks: +1, -0

A number is increased by x%, to get back to the original number, it is to be reduced by :

Solution:

(b) Cumulative % change

= a + b + { a b } /{ 100 }

Cumulative change to be 0
So

a+ { b } + { { ab } } /{ 100 } = 0

Here

a = x%

\ x + b + { x b } /{ 100 } = 0

⇒ b ( 1 + { x }/ { 100 } ) = - x

{ b } = { - { x } ( 100 ) }/ { 100 + { x } } = { - 100 { x } } /{ 100 + { x } }

– ve sign means decrease
So we need to decrease the number by

{ 100 x }/ { 100 + x } \%

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