A starts a business with a capital of Rs. 5,000. B joins in the business with Rs.2000 after some time. For how much period does B join, if the profits at the end of the year are divided in the ratio of 3 : 1?  Choose the correct choice:
A) 5 months B) 6 months C) 7 months D) 10 months E) None of these
Explanation :   Let B joins for x months. Then   A:B = 5000*12 : x* 2000 = 3 : 1   =&gt; 5*12 : 2x= 3 : 1   =&gt; 5*12/ 2x = 3/1= 
<gadget id="calculator">3/1</gadget>
<output>3</output>
3=&gt; 5*4 /2x = 1   =&gt; 10/x = 1   =&gt; x = 10. Answer : Option 10 months
<result>D</result>
A starts a business with a capital of Rs. 5,000. B joins in the business with Rs.2000 after some time. For how much period does B join, if the profits at the end of the year are divided in the ratio of 3 : 1?