Step-by-step explanation:
cup A = 60% of milk
= 60% Ă— 1600 ml
= 960 ml
cup B = 1600 ml - 960 ml
= 640 ml
milk drank from cup A
= 40% Ă— 960
= 384 ml
milk drank from cup B
= 70% Ă— 640
= 448 ml
how much more milk from cup B had been drank ?
= 448 ml - 384 ml
= 64 ml