The old profit-sharing ratio of A, B and C is 1:4:5. When C retires, the new ratio of A and B becomes 2:3. What is the gaining ratio of A and B?

Correct answer: 3:2

Under the old ratio, A’s share was \(\frac{1}{10}\) and B’s share was \(\frac{4}{10}\). Under the new ratio of 2:3, A’s share becomes \(\frac{4}{10}\) and B’s share becomes \(\frac{6}{10}\). Thus, A’s gain is \(\frac{4}{10}-\frac{1}{10}=\frac{3}{10}\), while B’s gain is \(\frac{6}{10}-\frac{4}{10}=\frac{2}{10}\). Therefore, the gaining ratio is 3:2. Exam tip: Calculate gaining ratio by subtracting each partner’s old share from the new share; do not use the new ratio directly.