数学有一题是说小明去度假,一共有11天是下雨的,一般呢要是上午下雨下午就不下,反之亦然。在度假期间有18天上午是没下雨的有20天下午是没下雨的(数字记不清了),请问小明一共有几天假期。 11 = 5+6=4+7=3+8=2+9=1+10=0+11 So the difference between sunny AM and sunny PM has to be 1, 3, 5, 7, 9 or 11. Therefore, it is possible to have 18 sunny AM and 21 sunny PM. In that case, the total days in Ming's vacation is 18 + 7 = 25. Note: you only need to count either the numbers of AM or PM, but not both. -- by 会员 sdcar2010 (2010/12/28 13:42:26)
it's well done! |