A man ordered 4 pairs of red socks and some additional pairs of grey socks. The price of the red socks per pair was twice that of the grey socks. When the salesman entered the order, the number of pairs of the two colours had been interchanged, which increased the bill by 25 percent. Find the ratio of the number of pairs of red socks to the number of pairs of grey socks in the original order.
A1:4
B2:3
C1:2 ✓ Correct
D1:3
Correct answer: (C) 1:2
Explanation
Red to grey pairs are in the ratio 1:2.
Let grey price = 1, red price = 2, grey pairs = g.
Original bill = 4 x 2 + g x 1 = 8 + g.
Swapped bill = g x 2 + 4 x 1 = 2g + 4 = 1.25(8 + g).
2g + 4 = 10 + 1.25g gives g = 8, ratio = 4:8 = 1:2.
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