A positive number when decreased by 4 is equal to 21 times the reciprocal of the number. The number is ?
A. 3
B. 5
C. 7
D. 9
Answer: Option C
Solution (By Examveda Team)
Let the number be xThen,
$$\eqalign{ & \Leftrightarrow x - 4 = \frac{{21}}{x} \cr & \Leftrightarrow {x^2} - 4x - 21 = 0 \cr & \Leftrightarrow \left( {x - 7} \right)\left( {x + 3} \right) = 0 \cr & \Leftrightarrow x = 7 \cr} $$
This Question Belongs to Arithmetic Ability >> Problems On Numbers
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