A man sells a book at 5% profit. If he had bought it at 5% less and sold it for Re 1 less, he would have gained 10%. The cost price of the book is  Select:
A) Rs 200
B) Rs 150
C) Rs 250
D) Rs 240
E) None of these
Let the C.P of the article be Rs X   Profit = 5%   Therefore, S.P. = X + 5 % of X = 21X / 20   If C.P would have been (X - 5% of X), i.e.,   Rs 19 X / 20 and S.P would have been Rs [ (21 X / 20) - 1 ],   Then, gain % = 10 %   Therefore, [ { ( 21 X / 20) - 1 } - 19 X / 20 ] / (19 X /20 ) x 100 = 10   (2 X - 20 / 19 X) x 100 = 10   =&gt; X = 200   Rs 200NSWER:Rs 200
<result>A</result>
A man sells a book at 5% profit. If he had bought it at 5% less and sold it for Re 1 less, he would have gained 10%. The cost price of the book is