Discuss Forum
1.
By selling a book for TK. 56, gain is as much percent as it costs in taka. The cost price is :
- A. TK. 280
- B. TK. 280
- C. TK. 280
- D. TK. 280
Answer: Option B
Explanation:
Let cost price Tk. x
x + x/100 × x = 56
100 x + x2 = 5600
x^2 + 100x - 5600 = 0
x^2 + 140 x - 40 x - 5600 = 0
x ( x + 140) - 40 ( x + 140) = 0
( x + 140) ( x - 40) = 0
x = - 140 ( not acceptable)
x = 40
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