A, B and C enter into partnership. A invests some money at the beginning, B invests double the amount after 6 months, and C invests thrice the amount after 8 months. If the annual gain be Rs.21000. A's share is?  Choices
A) 2999  B) 2778  C) 7000  D) 2889  E) 6612
x* 12 : 2x* 6: 3x* 4   1:1:1   1/3 * 21000= 
<gadget id="calculator">1/3 * 21000</gadget>
<output>7_000</output>
7000   Answer:7000
<result>C</result>
A, B and C enter into partnership. A invests some money at the beginning, B invests double the amount after 6 months, and C invests thrice the amount after 8 months. If the annual gain be Rs.21000. A's share is?