Question

4. By selling a book for 250, Sonu gains 25%. What is the C.P. of the book?
5. Rohit sold his wrist-watch for 1280 losing thereby 20%. Find the amount he paid for purchasing the
watch.
6. A bookseller buys paper at 50 per ream. At what price per quire should he sell it so as to gain 20%?
(Hint. 1 ream = 20 quiresl​

Answer 1

Cost Price of Book = Rs 200 , Amount paid for purchasing the watch = 1600

Step-by-step explanation:

By selling a book for 250, Sonu gains 25%

Cost Price = C

Gain = (25/100)C = 0.25C

Selling Price = C + 0.25C = 1.25C

1.25C = 250

=> C = 200

Cost Price of Book = Rs 200

Rohit sold his wrist-watch for 1280 losing thereby 20%

Let say Rohit Paid = P

Loss 20%  = (20/100)P = 0.2P

Selling Price = P - 0.2P = 0.8P

0.8P = 1280

=> P = 1600

Amount paid for purchasing the watch = 1600

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Answer 2

Cost price is 200

CP is 41.666

Cost price is 1600

Step-by-step explanation:

4. Selling price of a book = 250

Cost price of the book ,

125% = 250

100% = $\frac{250}{125}\times 100$

100% = 200

Cost price is 200

5. Rohit sold this watch, sp = 1280

Loss of 20% ,

80% = 1280

100% = $\frac{1280}{80}\times {100}$

100% = 1600

Cost price is 1600

6. Cost price , cp = 50

20% gain,

120% = $\frac{50}{120}\times 100$

100 = 41.6666

CP is 41.666