Question

A bookseller sells a book at a profit of 10%. if he had bought it at 4% less and sold it for rs.6 more, he would have gained 18 3/4% . what did cost him?

Answer 1

Let the C.P of the book = ₹ x

gain = 10%

S.P  =110x/ 100

If he had bought it at 4% less and sold it for Rs 6 more,

C.P=96x/ 100

S.P  =(110x/100)+6

Gain=((110x/100)+6)− 96x/100

= (14x/100)+6

Now, the gain =18 3/4%=75/ 4%

Therefore, 

(14x/100)+6=(96x/100)×75/400

(14x/100)+6=(96x/4)×3/ 400

14x+600=(96x/ 4)×3/ 4

14x+600=6 x(×3)

14x+600=18x

18x-14x=600

4x=600

x=150

The C.P of the book is ₹ 150

Answer 2

Let assume that fast of all

C.p =100

S.p=110

Now take if case

C.p =96

S.p=(cp+gain)=96×118.75%=114

Look that cp & sp comes twice so you must compare sp

Different sp =1st sp - 2nd sp=4%

4% comes =6

100% come =?

Cross multiply 600/4=150. (ans)

We know cp always 100%...