A started a business with Tk 24000 and was joined afterward by B with Tk 36000. After how many months did B join if the profits at end of the year are divided equally?

Question: A started a business with Tk 24000 and was joined afterward by B with Tk 36000. After how many months did B join if the profits at end of the year are divided equally?

Solution:
Suppose, B invested after x months

ATQ,
24000 × 12 = 36000 × (12 - x)
⇒ 24 × 12 = 36 × (12 - x)
⇒ 12 - x = (24 × 12)/36
⇒ 12 - x = 8
⇒ x = 4