During the 1st month after opening of a new shoping home,sales were $72 million.Each subsequent month,sales declined by the same fraction.If the sales during the third month after the opening totaled $18 million what is that fraction??

72, 36, 18, 9, ...
ans: 1/2 (50% decrease each month)

for more explain ...1/2 of 72 is 36. 1/2 of 36 is 18. the answer is 1/2