Pipes A and B can fill a cistern in 9 and 72 minutes respectively. They are opened an alternate minutes. Find how many minutes, the cistern shall be full? Choose the correct choice from the following options:
A) 13
B) 12
C) 16
D) 18
E) 19
:   1/9 + 1/72 = 1/8   8 * 2= 
<gadget id="calculator">8 * 2</gadget>
<output>16</output>
16.Answer:16
<result>C</result>
Pipes A and B can fill a cistern in 9 and 72 minutes respectively. They are opened an alternate minutes. Find how many minutes, the cistern shall be full?