A man ordered 4 pairs of black socks and some pairs of brown socks. The price of a pair of black socks is double that of a brown pair. While preparing the bill the clerk interchanged the number of black and brown pairs by mistake which increased the bill by 50% . The ratio of the number of black and brown pairs of socks in the original order was = ?

A. 2 : 1

B. 1 : 4

C. 1 : 2

D. 4 : 1

Answer: Option B

Solution(By Examveda Team)

	Black	:	Brown
Pairs	4	:	x
Price	2	:	1
	8	:	x

Original bill = 8 + x

	Black	:	Brown
Pairs	x	:	4
Price	2	:	1
	2x	:	4

New bill = 2x + 4
According to the question,
$$\eqalign{ & \therefore {\text{3}}\left( {8 + x} \right) = 2\left( {2x + 4} \right) \cr & \Rightarrow 24 + 3x = 4x + 8 \cr & \Rightarrow x = 16 \cr & \therefore {\text{ Brown pairs}} = 16 \cr & \therefore {\text{Black pairs}} = 4 \cr & \therefore {\text{Ratio}} \Rightarrow 1:4 \cr} $$