北美3/4体会+鸡经

hellokelly

(PS) two integers x and y, both their tens digits are 6, how many variations in tens digit of 2x+2y? 我选 B 4

how todeal with thisone?

cloverzoe

好厉害~

wangxiaoqing

b^2/2+1, not necessary, because b can be odd also

还有a^2/2－1, fine because a can only be even

cypress__ye

谢谢分享

maksimova

a^2/2－1可能为-1，-1就不是奇数了吧？

ningninggmat

Thanks LZ!

(PS) known that a&b are integers, a-b and a/b are both evens, ask
which of following must be odd? 里面有b^2/2+1, 还有a^2/2－1，挣扎了半天最后选第一个了

This one should be a^2/2-1, right?

ningninggmat

因为1984 is a leap year,是闰年，有366天，那3年的总天数应该多出来一天啊？

不是应该（365*3 + 1）/7 余4吗？那1987年6月21日就是星期一了？

我太笨，麻烦NN指点我错在哪了？

多出来一天是在1987年2月29号，所以已经过去了, "1984 is a leap year,是闰年" means there are no leap year in next 3 years.

sacrylin

Thanks