Pipes A and B can fill a cistern in 8 and 56 minutes respectively. They are opened an alternate minutes. Find how many minutes, the cistern shall be full?
Choose the correct option:
A) 13 B) 14 C) 16 D) 18 E) 19
:   1/8 + 1/56 = 1/7   7 * 2= 
<gadget id="calculator">7 * 2</gadget>
<output>14</output>
14.Answer:14
<result>B</result>
Pipes A and B can fill a cistern in 8 and 56 minutes respectively. They are opened an alternate minutes. Find how many minutes, the cistern shall be full?