'A' starts a business with Rs. 21000 and later 'B' joins him with Rs.36000 after how many months did B join if the profit is distributed in an equal ratio?

5

                          A       :        B

Inv.          →   21000   :     36000

Inv. ratio  →      7        :       12

Time         →     12       :       t       

Profit        →     1         :       1               (given)

Here,

(Profit = Inv. × time)

⇒ \(\frac{1}{1}\) = \(\frac{7\;×\;12}{12\;×\;t}\)

⇒ 12 t =  7 × 12

⇒ t = 7

Hence, B invest his capital for 7 months,

So, B joined after ( 12 - 7 ) = 5 Months