A started a business with an investment of Rs. 45,000 and B joined later with Rs. 5,400. After one year, the profit was shared between A and B in the ratio 2:1. How many months after A did B join the business?

Explanation

The profit ratio corresponds to the product of investment and time. For A: 45,000 × 12 months; for B: 5,400 × x months. Setting the ratio 45,000 × 12 to 5,400 × x equal to 2:1, we get x = 5 months. Since the total time is 12 months, B joined 12 - 5 = 7 months after A.