 
 <translate> Question. A pipe can fill a cistern in 20 minutes whereas the cistern when fill can be emptied by a leak in 60 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 17 minutes
(B) 87 minutes
(C) 30 minutes
(D) 27 minutes
(E) 11 minutes
Answer. (C)
What step-by-step reasoning justifies that answer? <hau> Tambaya. Bututun zai iya cika madatsar ruwa a cikin minti 20 yayin da madatsar ruwa lokacin da aka cika za a iya zubar da shi ta hanyar zubewa a cikin minti 60. Idan aka buɗe bututun biyu, ka san lokacin da rijiyar za ta cika? Zaɓuɓɓuka: (A) Minti 17 (B) Minti na 87 (C) Minti 30 (D) Minti 27 (E) Minti goma sha ɗaya Amsa wannan. (C) da kuma Wane bayani ne ya nuna cewa hakan gaskiya ne? 