A business

Two people, A and B starts a businesses. A began a business with $ 21000 and is joined afterwards by B with $ 36000. After how many months did B join, if the profits at the end of the year are divided equally?

Correct answer:

n =  5

Step-by-step explanation:

$$\begin{gathered} 21000\cdot 12=(12-n)\cdot 36000 \\ 21\cdot 12=(12-n)\cdot 36 \\ 36n=180 \\ n=\frac{180}{36}=5 \\ n=5 \end{gathered}$$

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