A positive number when decreased by 4 is equal to 21 times the reciprocal of this number The number ...........

Quantitative Aptitude (CGL) Number System

A positive number when decreased by 4, is equal to 21 times the reciprocal of this number. The number is

Suppose the number =x;
x-4 = 21*(1/x); => x²-4x-21=0;
x²-(7-3)x-21=0;
x²-7x+3x-21=0; => x(x-7)+3(x-7)=0;
(x-7)(x+3)=0; => x=7, -3

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