Re: [計量] 一題印度機經
※ 引述《julie331 (來吉)》之銘言：
: Given that (x,y) are ordered pairs, such that 0<=x<=10 and y<=x.
: How many such pairs are possible?
: 印度人給的答案是66
: 可是我光甚麼是ordered pairs就不太了解了
: 更不清楚要怎麼算出答案
: 不知道有沒有好心的強人能告訴我??
: 太感謝了
By Wikipedia
The pair is "ordered" in that (a, b) differs from (b, a) unless a = b.
n| 1 2 3 ... 11
-------------------
x| 0 1 2 ... 10
-------------------
y| 0 01 012 ...
where n means the number of pairs
Total= (1+11)*11/2=66
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