Question

Assume that for a certain product, brand a has 15% market share, brand b has 20% market share, and brand c has 65% market share. a new brand, brand d (d for dominant :) ), enters the market and captures 30% of the market. the total market has not grown. if brands a, b, c all lost share by the same relative amount, then what percent of the market does brand b have now?

Answer 1

Brand B market share is now at 14%

100 = 30 + (15-3x) + (20-4x) + (65-13x)
100 = 130-20x
20x = 130-100
x = 30/20
x = 1.5

b = 20-4*1.5
   = 14