A person ordered 5 pairs of black socks and some pairs of brown socks. The price of a black pair was thrice that of a brown pair. While preparing the bill, the bill clerk interchanged the number of black and brown pairs by mistake which increased the bill by 100% . What was the number of pairs of brown socks in the original order?
- A10
- B15
- C20
- D25Correct
Explanation
Let the number of brown pairs be x. Let the price of one brown pair be 1 unit. Then the price of one black pair is 3 units.
Original Bill Calculation: Price of 5 black pairs = 5 multiplied by 3 = 15 Price of x brown pairs = x multiplied by 1 = x Total Original Bill = 15 + x
Incorrect Bill Calculation (quantities interchanged): Number of black pairs = x Number of brown pairs = 5 Price of x black pairs = 3x Price of 5 brown pairs = 5 Total Incorrect Bill = 3x + 5
According to the problem, the incorrect bill increased by 100 percent, meaning it is double the original bill. 3x + 5 = 2 multiplied by (15 + x) 3x + 5 = 30 + 2x 3x minus 2x = 30 minus 5 x = 25
The number of pairs of brown socks is 25. The correct option is D.
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